The best thing about Firefox is that it's highly customizable, either through plugins or internal settings. In fact, there are many settings that are not exposed through the Tools > Settings menu. To change these settings you need to tweak the prefs.js file where Firefox stores all it's internal settings. But it's difficult to edit the prefs.js file and it's easier to change these settings through the browser window.
Type about:config in the address bar and press Enter, and you'll see all the settings currently enumerated in prefs.js, listed in alphabetical order. To narrow down the hundreds of configuration preferences to just the few you need, type a search term into the Filter: bar. Click the Show All button or just clear the Filter: bar to get the full list back again. But before you start toying with the settings in about:config, remember to backup the prefs.js file.
Once you have a backup of prefs.js, fireup about:config and change the settings which you want to from the list.
1. When you are typing an URL in the Address Bar (Smart Location Bar), a dropdown list of suggestive URLs becomes visible. The default number of URLs that are shown is 12, but you can configure that using the browser.urlbar.maxRichResults key. Double click on that and input the number of URLs that you want Firefox to show. If you want to disable this feature, set the value to -1.
2. If you are not satisfied with the default Firefox color profiles, it also has an Advanced Color Profile feature available. But enabling this make Firefox a bit sluggish. So if you are not concerned about performance but image quality then you can enable this feature by modifying the gfx.color_management.enabled key. It's default value is set to False, you need to change it to True.
3. When you have opened too many tabs in Firefox, it shows a scrolling bar so that the 100px width is conserved. If you don't like this feature and would like Firefox to display all the tabs, however small they are, you can disable it using the browser.tabs.tabMinWidth key. The default value of this key is 100, to disable it you need to set it to 0, to display tabs of different width you can set a value lower than 100 (example : 75).
4. Every tab on Firefox has a Close X button on it. Some people love them, some don't. You can change it's behavior using the browser.tabs.closeButtons key. It's default value is set to 1. To display a close button on the active tab only set it's value to 0, to display close buttons on all tabs set it to 1, to display a single close button at the end of the tab strip set it to 3 and if you don't want to display any close button at all set it to 2.
5. If you try to open a bookmark, Firefox usually replaces any existing tabs with the newly opened pages. So avoid this you need to modify the browser.tabs.loadFolderAndReplace. It's default value is True, to open bookmarks by appending new tabs to the existing window instead of overwriting existing ones, you need to set it's value to False.
6. Firefox automatically save your session every 10 seconds so that, in case the browser crashes, it can restore all your tabs. While this is a useful feature, some users find it irritating. To disable this function, toggle the value of browser.sessionstore.enabled to False, it's default value is True.
7. When you are browsing in a fullscreen mode, the Firefox toolbar by default is set to autohide. It appears only upon mouseover. If you want to view the toolbar at all times, set the value of browser.fullscreen.autohide to False. To autohide once again, set it back to True.
8. When "Save Link As..." is being used, Firefox request the content disposition header from the URL so as to determine the filename. If the URL did not deliver the header within 1 sec, Firefox will issue a timeout value. This could happen very frequently in a slow network connection environment. To prevent this, set the Browser.download.saveLinkAsFilenameTimeout to any value higher than 1000, which is the default value and equals 1 second (1 second = 1000 millisecond).
9. If you are a developer and use the View Source function often, then you can as well make Firefox open the source file in your favorite Editor. For this you need to change the view_source.editor.external to True, it's default value being False. And then change the value of view_source.editor.path, which would be set to blank by default, to the path of your favorite editor.
10. When you are installing a Firefox add-on, you usually have to wait for several seconds before the installation process starts. To avoid this, set the value of security.dialog_enable_delay to 0 to start the installation immediately. It's default value would be set to 2000 (2 seconds).
11. When minimized, Firefox allows the Windows memory manager to swap out some of Firefox's physical memory space to disk. This allows other programs to use the physical memory that Firefox was hitherto using. By default this feature is turned off. To enable this change the value of config.trim_on_minimize to True.
12. Want to use an extension that is not compatible with your version of Firefox? Well, although it's not recommended, you can do it by right clicking on a blank area and select New > Boolean, then enter extensions.checkCompatibility in the first field and False in the second field. Then create another value by again right clicking and selecting New > Boolean, enter extensions.checkUpdateSecurity in the first field and False in the second field.
13. Unlike it's previous versions, Firefox 3 backup the bookmarks file in places.sqlite rather than the usual bookmarks.html. But these are not compatible with all browsers, so to make Firefox save the bookmarks as bookmarks.html, change the value of browser.bookmarks.autoExportHTML to True.
14. To increase offline cache so that, in case you don't have access to internet connection most of the time, you can still continue to work offline, change the value of browser.cache.offline.capacity from 512000 (in KB) to any higher value.
15. Many of us use the in-page search of Firefox. Now this in-page search is not case-sensitive. To avail of the case-sensitive in-page search feature, set the value of accessibility.typeaheadfind.casesensitive to 1. It's default value is 0 which sets it for case-insensitive search.
16. If you double-click on a single word on a web page, Firefox usually also includes a trailing blanks space. If you don't want this trailing blank space to be included in your selection, set the value of layout.word_select.eat_space_to_next_word to False.
17. If you are not satisfied with the default zoom level and want to see something by zooming it even more, then all you need to do is set the value of zoom.maxPercent, which has a default value of 300, to any higher value for a greater zoom-in. For a greater zoom-out, change the default value of 30 for the zoom.minPercent to anything less.
18. You can set the URL bar to Autofill when you are typing an URL. To do this, you need to change the value of browser.urlbar.autofill to True.
19. Unlike in Windows or Mac, Firefox does not select the complete URL when you click on it in Linux. Instead it places the cursor at the insertion point. If you feel that Firefox is discriminating you as a respectable Linux user, then change the value of browser.urlbar.clickSelectsAll to True.
20. When you are using the search box at the top right hand corner of the browser, it would display the search results in the current tab. If you want Firefox to behave well and not do this again, simply change the value of browser.search.openintab to True to open the search results in a new tab.
21. To change the number of simultaneous connections Firefox will make at any one time to any number of Web servers, change the value of network.http.max-connections, which has a default value of 24, to anything between 24 and 32. Although people do use values upto 64, but any value above 32 really does not cause any significant changes.
22. To enable "pipelining", an experimental feature to speed up the loading of most web pages, set the value of network.http.pipelining to True. Along with that, change the value of network.http.pipelining.maxrequests to anything between 16 and 128, although I would personally suggest 16. And if you are using a proxy, be sure to change the value of network.http.proxy.pipelining to True.
23. To enable spell check for single line text boxes, which is enabled for multi line text boxes by default, all you need to do is change the value of layout.spellcheckDefault to 2. To disable spell check altogether, set it to 0. Use spell check to avoid any Freudian slips in your documents.
24. By default, Firefox waits 250 millisecond before it starts rendering a page. If you want Firefox to start rendering any webpage immediately, change the value of nglayout.initialpaint.delay to 0.
25. In Firefox 3, a script is given a time period of 10 seconds to respond, after which it issues a unresponsive script warning. If you are on a slow network connection and would like to increase the script execution time, all you need to do is change the value of dom.max_script_run_time to any value greater than 10 (which is the default value).
26. This is mainly for Windows users. By default, Firefox 3 automatically initiates a virus scan a downloaded file with the default anti-virus application. So in case you are downloading a large file, it could take a long time for the whole scanning process to complete. To disable the anti-virus scanning you need to change the value of browser.download.manager.scanWhenDone to False.
27. Web pages (and web servers) can ask a browser to automatically refresh a page after a given timeout. This can be helpful (as in the case of a webpage whose content is updated constantly) but it also can be irritating. To prevent this you need to change the value of accessibility.blockautorefresh to True. It with disable refreshing a page automatically when is present (or Refresh HTTP headers), display a browser message indicating the refresh and allow the user to follow it manually.
28. Firefox 3 usually allows the history sidebar to group pages by browsing session as well as by last visit, which can be a useful distinction when trying to find a previously-visited page. But if you like the Firefox 2 look better than this, then change the value of browser.history.showSessions to False.
29. In Firefox 3, extensions use one of the following approaches for updates: an SSL-encrypted update URL, no update URL at all, or an update key/hash for verifying the validity of the update. If an extension does not use one of the mentioned methods for securing updates, Firefox will prevent it from being installed. So if you want to install some extension which does not uses these update methods, simply set the value of extensions.checkUpdateSecurity to False.
30. Firefox 3 by default accept cookies from a site irrespective of whether you have previously deleted cookies from that site or not. To prevent this, simply set the value of network.cookie.blockFutureCookies to True, it's default value being False.
31. By default Firefox 3 automatically fills the sign-in forms with known usernames and passwords on appropriate sites. If you don't want this for security reason, set the value of signon.prefillForms to False and Firefox would act as though there are multiple usernames/password pairs remembered for the form (fill password after username has been manually typed).
If you liked this post, then be sure to check out the 50+ Essential Firefox Extensions For Designers and Developers.