Firefox Tweak Guide

[Page 5] Firefox Settings (Pt.2)


Tracking: New to Firefox 21.0, this feature was first introduced in Firefox 4.0, and was then moved from the Advanced section of the Options to the Privacy section to make it more prominent. Basically, some sites track your browsing behaviour for advertising purposes for example. This is primarily done by third party advertisers on a site. There are three available options here. If the 'Tell sites that I do not want to be tracked' option is ticked, it informs websites that you do not want your browsing behavior to be tracked while visiting them. If you wish to be tracked, select 'Tell sites that I want to be tracked'. Complying with your request not to be tracked is entirely voluntary, so selecting the option to not be tracked does not actually force websites to stop tracking you if they wish to keep doing so. Note that blocking tracking will not disable cookies or other stored site preferences, login details, etc. As of Firefox 21.0, a third option 'Do not tell sites anything about my tracking preferences' has been added, so that if for some reason you don't want to reveal any particular preference for tracking, you can select this option instead.

History: By default, Firefox will keep a history of your browsing habits, saving such details as which websites you've visited over the past 90 days, which files you've downloaded, any form data entered, search terms used, and any custom preferences for websites. This is not something to be concerned about in general, as none of it is reported back to anyone, and most of it is used to improve your browsing experience. However if you don't wish Firefox to keep any such records on your drive, in the History drop down box you can select either 'Never remember history' which is the same as the Private Browsing Mode feature covered later in this guide, or you can select 'Use custom settings for history', which is generally recommended and covered in more detail below:

Permanent Private Browsing mode: If ticked, this option will force Firefox to automatically start in Private Browsing Mode each time Firefox is launched. Private Browsing Mode is covered in full detail under its own area in the Features, Tips and Tricks section.

Remember my browsing history: The addresses of the sites you visit in Firefox will be held for 90 days if this option is ticked. If you don't want this history kept untick this box. Alternatively, keep it ticked but use Private Browsing mode for the times when you don't wish certain sites to be recorded in your browsing history. The reason you may want to keep any history of the pages you have visited is that aside from being of use when you want to revisit a page you may not have bookmarked, but which you cannot recall, browsing history can also be utilized in other ways. For example, you can search your history and bookmarks dynamically just by typing in any letters or words in the Address Bar, and the results will be instantly displayed in a drop down box beneath it. This feature is covered in more detail under the Awesome Bar area of the Features, Tips and Tricks section.

Remember download history: Every time you download a file using Firefox, it keeps a history of the file in a list in the Downloads window, which appears during file downloads, or by clicking the Firefox button and selecting Downloads. If you don't wish this history to be kept, untick this box. For many people there's no real reason to keep a download history, and indeed it may also make the Downloads window more responsive if no such history is kept. However the Search functionality and file display features in the Downloads window, all covered under the Downloads area of the Features, Tips and Tricks section, might give you one reason to keep this option enabled.

Remember search and form history: If this box is ticked Firefox will save any details you enter in online forms as well as in the search bar. Unless you fill in such forms very often, for security and privacy purposes I recommend having this box unticked. Note that this option does not need to be enabled to save your passwords/login details for sites, that feature is covered under the 'Remember passwords for sites' setting later in this guide.

Accept cookies from sites: Cookies are small files which are placed on your computer by various websites. These hold information which can be referred to by the website the next time you visit, such as any customizations you may have selected for that site, or your username for a forum, or which ads on a site you have already been shown. Cookies are mostly harmless, and often have legitimate uses, so blocking them altogether is not wise. Furthermore, some sites will not function correctly if their cookies are blocked.

The 'Accept third-party cookies' option can be safely unticked however, as this relates to cookies provided not by the site which you are viewing, but by third parties providing additional content on that site - typically this means things like advertisements, videos or maps which aren't vital to the proper functioning of the main site.

If you run into problems, or if you have the time, you can click the Exceptions button and allow or block individual sites from placing a cookie on your machine. That way you can block all cookies for example (by unticking the two options above), but allow them for specific trusted sites which would otherwise not function properly.

To get an idea of the types of cookies already on your machine, click the 'Show Cookies' button and you can individually remove any which look suspicious. However if in doubt, leave the cookies untouched - the best way to scan for bad cookies is to regularly use a malware/adware scanner, which is covered in the PC Security chapter of the TweakGuides Tweaking Companion.

Finally, the 'Keep until' option relates to how long cookies are retained on your drive. Since cookies can hold useful information, I recommend the 'they expire' option be chosen, which will keep cookies for as long as they are needed. If you value privacy above all else and want cookies cleared every single time you close Firefox, then select the 'I close Firefox' option, but this will mean you will lose all customizations related to cookies each time you close Firefox . If you want to make the choice on a case-by-case basis (which is not recommended), select the 'ask me every time' option.

Clear history when Firefox closes: When this box is ticked, the Settings button to the right is ungreyed and you can click it to customize which particular aspects of your browsing history are cleared when Firefox closes. On a machine which is shared with a lot of other people, such as a public machine, you should enable this option and tick all available items as added protection. On a personal machine which you don't share with others, or if you have your own separate password-protected user account on a shared machine, I don't recommend clearing history each time Firefox closes, as it reduces browsing efficiency and convenience, and may also increase Firefox closing times.

To clear any elements of your history at any time, click the Firefox button, and under the History item select 'Clear Recent History' to open a new window. This allows you to select which period of time for which to clear your history, such as 'Last two hours' or 'Today', or select Everything to clear all history stored to date. To customize precisely what is cleared each time, click the Details item and select which component(s) to clear: 'Browsing and Download History' is generally fine to clear, as is 'Form & Search History' - removing these will have minimal impact on convenience in most cases. Clearing Cookies, 'Site Preferences' and 'Active Logins' will remove all site-specific customizations and log you out of any sites you were previously automatically logged into. Clearing the Cache may reduce browsing speed, especially if you aren't on a fast Internet connection, as Firefox will need to re-download all previously cached website elements when you next visit them - clear the cache less frequently if possible. When you've finished making your selections, click the 'Clear Now' button to clear all selected elements of your history from your drive for the time period you specified.

Ultimately, if you're genuinely concerned about leaving any traces of your activity on a PC each time you use Firefox, use Private Browsing Mode at all times, or see the Portable Firefox tip at the Conclusion of this guide for more useful solutions.

Location Bar: The Location Bar is also known as the Address Bar or Awesome Bar - see the Awesome Bar area of the Features, Tips and Tricks section for more details. Here you can select which aspect of your stored data is used for the search functionality of the Location Bar. By default if you enter any text in the Location Bar it will show the closest result(s) from your browsing history and bookmarks. If instead you wish the Location Bar to just search through your stored browsing history, select History; if you just want it to search through your saved bookmarks, select Bookmarks. If you want this Location Bar functionality disabled such that it conducts no searches and shows no results, select Nothing instead.


Warn me when sites try to install add-ons: I strongly recommend you tick this option as it prevents websites from attempting to install add-ons without your full knowledge and consent. With this option ticked, before any site attempts to install an add-on, Firefox will block such attempts and give you prominent notification of what it is trying to install. If in doubt, cancel out of the installation and do some research to find out more. Most add-ons are unnecessary at best and can reduce performance, some are actually malicious or will spy on you browsing behavior. Click the 'Exceptions' button to view the sites which are allowed to install Firefox add-ons. By default the Mozilla-run sites and will be listed here - if any untrusted or unknown sites are also listed, highlight and remove them.

The most commonly used add-on software you will need installed when viewing certain websites is Flash Player. For other potentially useful add-ons for Firefox see the Add-on Manager area in the Features, Tips and Tricks section, as well as the Add-ons section of this guide.

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Block reported attack sites: This setting allows Firefox to warn you if the site you are about to visit could potentially be a known 'attack site'; namely a site which attempts to use malicious scripts or other techniques to harm your PC, or send sensitive personal information about you to other parties without your permission. If you try to visit such a site, Firefox will raise a prominent warning stating 'Reported Attack Site' which comes up before you can even view the site's contents, and before anything is loaded up, keeping you safe from exposure to any malware on the site. I strongly recommend that this option always remain ticked as it's a valuable layer of protection against being exposed to such sites, though it's not a completely foolproof mechanism for protecting you when online.

Block reported web forgeries: Similar to the 'attack site' option above, this setting is part of Firefox's Phishing Protection feature. It will raise a prominent warning stating 'Reported Web Forgery' before the page can be loaded or viewed. Once again I strongly recommend enabling this option, as it adds another layer of protection against having your important data (such as bank account or credit card details) stolen if entered on a fraudulent site. As with the attack site protection, it is not foolproof, and should not be relied upon as the sole form of defense or a replacement for using common sense and vigilance.

Both these anti-malware protection and anti-phishing protection features in Firefox are automatically powered by the Google Safe Browsing Service, and there is no option here to change this behavior. This means that aside from maintaining a list of potentially harmful sites within Firefox itself and regularly updating it when online, when you visit a potentially harmful site, the browser may automatically connect to Google's servers to provide more detailed information about it. The link above gives specific details regarding its functionality in Firefox and may address any privacy concerns you have, but ultimately if you don't agree to this approach then your only recourse is either to completely disable the two option above, or see the browser.safebrowsing.provider preference in the Advanced Tweaking section. It is not recommended that you disable or alter these settings.

Passwords: If the 'Remember passwords for sites' box is ticked, whenever you enter a username and/or password on a web page, you will be given the option to save that username/password within Firefox. If you do so, the next time you go to the same site your password will be automatically filled in as a series of *****, along with any username. This speeds up logging into various sites, and means you don't have to remember all of your username/password combos, however it is also a significant security risk if you share a computer with others. Untick this option if using a shared or unsecured machine. If this box is ticked, the 'Remember password' prompt appears as soon as you enter a username/password in a login area, and will remain until either you choose an option or navigate away from it. It won't block your login progress, which allows you to see if your username/password is actually correct before you choose to remember it. When presented with options for saving your username/password, you can click the main button to save the password, or click the arrow and select one of the following from the drop-down box: 'Never remember password for this site' means that not only will your username/password not be saved, you will also never again be prompted to save a username/password for this site; or 'Not now', which means that the username/password will not be saved this time, but you will be prompted again the next time you attempt to login here.

To view the currently stored usernames and passwords (and the sites they relate to), click the 'Saved Passwords' button. This opens a window which shows every username you've saved on particular sites. To view the actual passwords for each site, click the 'Show Passwords' button at the bottom of the window, and this will reveal a new Passwords column. You can highlight specific entries and click Remove to delete any incorrect or unnecessary username/password combinations as required. If you want to protect yourself from others who may try to view your password list, tick the 'Use a master password' option under the main Passwords section of the options and then enter a master password - the more letters and numbers the password contains, the stronger it will be as indicated by the password quality meter at the bottom of the master password dialog box. Now whenever you click the 'Show Passwords' button you must first enter this master password to see all the passwords. There is also a search box in the Saved Passwords window, allowing you to find any site, password or username much more rapidly.

New to Firefox 4.0, the Warning Messages section has been removed from the Options, and some of these settings can now be found under the Advanced section of Firefox Options, or adjusted on a case-by-case basis as relevant warnings appear during normal browsing.


New to Firefox 4.0, Firefox Sync, formerly known as Weave, is designed to let users synchronize their history, bookmarks, passwords and open tabs across a range of devices. That way, you will get a consistent and continuous experience regardless of where you are using Firefox. This is done by holding your details on Mozilla's servers, linked to a specific account which you create for this purpose, which is then read from or written to by your various PCs or devices when you use Firefox on them.

New to Firefox 6.0, before you can use this feature, you'll need to click the 'Set Up Sync' item under the main Firefox button - it has been moved there in Firefox 6.0 to make it easier to find. Click the 'Create a New Account' button, and you will then need to provide a valid email address, a password for your new Sync account, and then select the server to which these details will be stored - the default 'Firefox Sync Server' is recommended unless you have details of a specific trusted server which you prefer. Agree to the terms of service and click Next. For security purposes, all of your private data is encrypted when stored on the Firefox Sync Server, and to decrypt this a special Sync key will be allocated to your account. Save this key, as losing it means you won't be able to Sync with other devices unless you create another new account, or generate a new key, in which case all of your previously stored Sync data will be erased. Finally, click the 'Sync Options' button, and you can edit both the Computer Name which is used to identify your machine/device in your Sync network, and also choose from the specific Firefox elements you wish to keep synced across your devices. Continue with the last few prompts until setup is complete - Sync is now automatically in effect.

New to Firefox 11.0, Add-ons can now also be synchronized across computers.

You can now manage your account and alter which items are being synced in the Sync section of Options. Importantly, you can add a device to your Sync network by clicking the 'Add a Device' link and following the prompts. To troubleshoot Sync-related issues, see here.



Always use the cursor keys to navigate within pages: When ticked, a flashing cursor will be shown on the web page. You can then use the arrow keys on the keyboard to move the cursor around, and you can also use the SHIFT key along with the arrows to highlight portions of text. Set to suit your taste, however note that firstly you may have to click on a page to initiate the cursor, and secondly, if enabled, this option may force a flashing cursor to appear on some web pages even without being clicked on, which may be annoying to some. If you just want to use this mode at certain times, use the F7 key to toggle it on or off as desired.

Search for text when I start typing: If this option ticked, as you start typing, a search box automatically appears at the bottom of the screen and initiates a search of the current page based on your input. If unticked, you will have to press the Find shortcut key (F3 or CTRL+F) to open the search box. I suggest you tick this option to begin with, and if you find it annoying then untick. See the Faster Searching area of the Features, Tips and Tricks section for more details of ways to speed up searching and how to customize this function.

Warn me when web sites try to redirect or reload the page: This option is designed to prevent sites from automatically redirecting or reloading the page without your permission. If that happens, a prompt will appear at the top of the screen indicating what has occurred and asks you whether you wish to allow this behavior or not. It is worth ticking this option to maintain greater control over your browsing, but it may get annoying as it also comes up on legitimate sites which reload/redirect.

Use autoscrolling: If ticked this option enables Autoscroll, letting you scroll the page quickly by first clicking the middle mouse button once, and then simply moving your mouse up or down. Untick it if you find it annoying.

Use smooth scrolling: If this option is ticked, when a page is scrolled up or down, either by using the Page Up or Page Down keys, or via the mousewheel, it scrolls more slowly and smoothly, allowing your eyes to better track your existing position to its new spot on the screen. This can make reading long passages of text easier, however it may also make some pages seem 'laggy' when scrolling them.

Use hardware acceleration when available: New to Firefox 4.0, if this option is ticked, Firefox will use Hardware Acceleration to improve the speed with which pages are displayed, utilizing your GPU (graphics card), if you have one, instead of your CPU. Windows Vista/7 benefits more fully from hardware acceleration than Windows XP, as under Vista/7 both Direct2D and Direct3D acceleration is enabled. Note that altering this setting requires a full restart of Firefox before the change is implemented.

To check the status of hardware acceleration in Firefox at any time, type 'About:Support' (without quotes) into the Address Bar and press Enter. At the bottom under the Graphics section, check the 'Direct2D Enabled' and 'DirectWrite Enabled' fields - these will say True if enabled, False if not. The 'GPU Accelerated Windows' field will show '1/1 Direct3D 10' or '1/1 Direct3D 9' depending on the level of Direct3D support enabled, or '0/1' if Direct3D acceleration is disabled. To test and compare your actual hardware acceleration performance after making any changes, first exit and restart Firefox, then run this test to see how many FPS you get with each configuration.

An unfortunate side-effect of enabling hardware acceleration in Firefox is that the text rendering method changes to one which some users will find displeasing. Fonts may appear blurry, overly thin, oddly spaced or inconsistently rendered across various sites. The easiest way to fix this issue is to disable hardware acceleration and restart Firefox - text rendering will now revert back to its original and familiar look. However this loses all the benefits of GPU hardware acceleration. A slightly better method of fixing this issue is to keep this option ticked, but set the gfx.direct2d.disabled preference to True - see the Advanced Tweaking section for details. This disables Direct2D acceleration while keeping Direct3D acceleration enabled. Another alternative is to keep this option ticked, and install the Anti-Aliasing Tuner add-on, which allows customization of font appearance, while keeping the full advantages of hardware acceleration. Open the Options for this add-on (under Firefox>Add-ons>Extensions), and try this suggested configuration: set Anti-Aliasing mode to ClearType and Rendering Mode to 'Natural Symmetric' for both text sizes, then tick all the 'ClearType Level' and 'Enhanced Contrast' boxes and set them to 100%. This will not be ideal, but you can experiment further to see if you can further customize text appearance to suit your taste.

Update: I have found in more recent versions of Firefox that completely disabling hardware acceleration actually provides the best performance on my desktop PC. With hardware acceleration enabled, my GPU would continually cycle between 2D and 3D clock speeds, and there would be periodic stuttering/pauses on certain pages, such as those with Flash video or heavy scripting. This is neither good for the GPU, nor good for overall smoothness of use. Therefore I recommend experimenting with disabling hardware acceleration to see if it improves overall performance for you, and it may also resolve certain GPU-related crashes being reported by some users.

Check my spelling as I type: If this option is ticked, the built-in Firefox spell checker will automatically check the spelling of any text entered in standard text input boxes on a page and underline in red any words which it believes are misspelled. You can then right-click on the word to see suggested spellings and select one, or you can add the word to the current dictionary used. I recommend that you enable this option, and remember that the default dictionary used depends on the particular language version of Firefox you're using. See the Features, Tips & Tricks section for more details of this feature.

Always check to see if Firefox is the default browser on startup: If this option is ticked, Firefox will check to see whether it is the default browser each time it starts. You should untick this option for fastest startup, and instead if you want to be certain that Firefox is your default browser, in Windows Vista/7 go to Windows Control Panel>Default Programs>Set Default Programs and select 'Set this program as the default' for Firefox. In Windows XP go to your Windows Control Panel>Add/Remove Programs. On the left hand side of the 'Add or Remove Programs' box, click the 'Set Program Access and Defaults' icon, select the Custom option, and under the 'Choose a default web browser' section select 'Mozilla Firefox'. Click OK to close, and now Firefox is your default browser. To confirm this, click the 'Check Now' button here, but again, be sure to leave this box unticked for optimal startup performance. Also go to Windows Control Panel>Internet Options, and under the Programs tab untick any option related to checking for or making Internet Explorer the default web browser. Do the same for any other browser(s) you have installed.

Data Choice

Enable Telemetry: If this option is ticked, anonymous data regarding your Firefox configuration and system will be sent to Mozilla, allowing them to improve Firefox's performance in the future. If you don't wish this data to be sent, untick this option.

Enable Firefox Health Report: New to Firefox 21.0, the Firefox Health Report (FHR), if enabled, collects and sends a range of Firefox performance information to Mozilla. Importantly, it also assists users to resolve their own problems by examining this information in the FHR Dashboard. To access the FHR Dashboard, type 'About:Healthreport' (without quotes) into the Address Bar and press Enter. The Dashboard provides statistics and tips which can give you an insight into what may be causing you problems in Firefox, or how to improve its performance on your system.

Enable Crash Report: If this option is ticked, any time Firefox crashes, the Mozilla Crash Reporter will open, and you can choose to submit a summary report on the crash to Mozilla. The Crash Reporter provides options allowing you to determine which potentially sensitive details you may wish to include/omit from the report, such as the address of the site you were browsing when Firefox crashed. This can help Mozilla to better detect and resolve genuine bugs in Firefox.

If you have privacy concerns about your data being shared with Mozilla by any of the above features, click the 'Learn More' link in this section to read their privacy policy.


Configure how Firefox connects to the Internet: This setting is very important, and if you need help configuring it correctly contact your Internet Service Provider (ISP). If configured incorrectly you will have problems accessing the Internet through Firefox or you may have relatively slow loading of pages. Click the Settings button, and for most people the 'No Proxy' option is appropriate, as the average home PC user does not go through a Proxy. If you have any doubts about whether you are behind a proxy or not, or you are on a networked machine, then select the 'Auto-detect proxy settings for this network'. If you are certain that you are behind a proxy, it is recommended that you select 'Manual proxy configuration' and specify your proxy settings for optimal performance, but you will require specific information from your ISP or Network Administrator to do this.

To potentially optimize your network connection usage and speed in Firefox regardless of your connection type, see the network.-related preferences in the Advanced Tweaking section.

Cached Web Content: The browser cache is a form of offline storage on your drive where Firefox holds website elements such as images, text, videos, ads etc. This speeds up browsing, because whenever you revisit a site, the stored version of the unchanged elements from that site are loaded from your drive as opposed to having to be redownloaded over the Internet. New to Firefox 4.0, by default Firefox now automatically handles the amount of drive space allocated to the cache, up to a maximum of 1GB. You can see the current amount of drive space used by the cache in this section, and if you tick the 'Override automatic cache management' box, you can manually specify the maximum amount of drive space allowed for the cache. A cache which is too small or set to 0 will increase page loading times, but similarly, a cache that gets too large may also reduce browsing speed, especially if you have a fast Internet connection but a relatively slow drive for example. In practice, allowing Firefox to automatically manage the cache is the preferred option for most users, however if you're running low on drive space, or find that browsing appears to slow down over time, click the 'Clear Now' button to clear the existing cache contents, and then manually set a lower limit for the cache, such as 250MB.

See the browser.cache.-related preferences in the Advanced Tweaking section for more ways to customize how Firefox handles the cache. Also see the 'Cached Files' area at the start of the Advanced Tweaking section for details of how to view the actual contents of your cache.

Tell me when a website asks to store data for offline use: You can specify whether to be prompted when a website explicitly wants to store data on your drive for offline use. This is not the same as the regular offline storage (cache) covered above - this is a feature which allows web applications to be specifically written so that they can be used when Firefox is not connected to the Internet. You should tick this option so that you are aware of when an application may wish to use this feature. You can see a list of the sites which have stored such data in the box below this option, and you can opt to remove any which you are not familiar with. You can also add specific exceptions if you know certain sites should always be allowed to use this functionality without requiring a prompt. Finally, you can adjust how much storage space Firefox allocates for offline files by changing the browser.cache.offline.capacity preference, or disable the feature using the browser.cache.offline.enable preference, as covered in the Advanced Tweaking section.


New to Firefox 12: Firefox now installs updates automatically and silently in the background by default. This is made possible if the optional Mozilla Maintenance Service is enabled during installation of Firefox 12 or newer. The service is set to Manual in Windows by default and hence normally consumes no resources, but it can be completely removed by going to Program and Features in the Windows Control Panel and uninstalling the 'Mozilla Maintenance Service' item.

Automatically install updates: If this box is ticked, Firefox will regularly check for updates and if the Mozilla Maintenance Service is installed and set to Manual, will automatically install any newer version of itself when detected. If you also tick the 'Warn me if this will disable any of my add-ons' box, Firefox will prompt you if an update is incompatible with your current add-ons. The automatic option is recommended for average users as it maintains maximum security by automatically keeping Firefox up-to-date at all times.

Check for updates, but let me choose whether to install them: If this option is ticked, you will be prompted when an update is detected; it will not be automatically installed in the background. This is recommended for medium to advanced users who wish to retain more control over the updating process. For example, you may want to delay the installation of certain updates whether due to issues with your current add-ons, or other known or potential problems with an update.

Never check for updates: If this option is ticked, Firefox will not check for updates, nor will it install any updates in the background. This is not recommended as it means running the risk of having an outdated and hence insecure version of Firefox.

Use a background service to install updates: If you have chosen to install the Mozilla Maintenance Service during installation of Firefox 12 or newer, and this box is ticked, then Firefox will automatically install any detected updates to itself silently in the background. If you don't want this silent update functionality, untick this box. You can go even further by removing the Mozilla Maintenance Service altogether as noted further above. If the Mozilla Maintenance Service is not installed, this box won't be shown at all.


Protocols: The options here are 'Use SSL 3.0' and 'Use TLS 1.0'. I recommend that you tick both options, as they use appropriate security protocols (SSL is Secured Sockets Layer and TLS is Transport Layer Security) to ensure secure transmission of data over the Internet. If one or the other is unticked, you may not be able to visit some sites. If you encounter any difficulties with a particular website, untick 'Use SSL 3.0' first, then untick 'Use TLS 1.0'. Avoid entering any personal data on sites which don't support these protocols, as all genuinely secure sites should support them.

When a server requests my personal certificate: This setting determines how Firefox reacts to a request by a website to present a Certificate. Certificates are used to verify identity and/or provide authorization for secure transmissions. You can choose 'Select one automatically' to allow Firefox to determine the appropriate Certificate to present, but this can potentially compromise your privacy. Select the 'Ask me every time' so that you are prompted to manually select a Certificate, and if in doubt, do further research before accepting a certificate request on a particular site.

View Certificates: Clicking this button brings up a box which allows you to add or remove various types of Certificates - those which are yours, those of others, those of web sites you visit, and those of authorities which verify certificates. In general you shouldn't need to change these settings unless you know what you're doing. This option is best used as part of researching the validity of a certificate.

Revocation Lists: CRL is your Certificate Revocation List - a list of Certificates which are no longer valid. Firefox can use such a list if you need to add one, however as with the other Certificate options in Firefox, this is not something you need to adjust unless you are familiar with this functionality.

Validation: OCSP is the Online Certificate Status Protocol, an online method to determine the validity of a Certificate. By default you should have the 'Use the OCSP to confirm the current validity of certificates' box ticked, along with the first option below it. If you want to manually specify a server, tick the second option below it and specify the server. If you want even more advanced security select the 'When an OCSP server connection fails, treat the certificate as invalid', however this can cause many problems, so is best left unticked unless you know what you're doing.

Security Devices: Clicking this button allows you to manage the tools which facilitate secure access in Firefox. There are two which are built into Firefox, but you can manage or use others which are installed on your system. Once again there is no need to change these settings unless you know exactly what you're doing and have specific needs.

Once you're done with all the settings, click OK to exit the Options window, and I also recommend closing all incidences of Firefox and restarting the browser to ensure all settings are applied properly.

The next section provides a range of details and tips on all the major features of Firefox.