I often write that the Mozilla Foundation's Firefox browser does thus and such, or doesn't do this or that other thing. What I mean is that the program has no menu command or preferences dialog box to give users control over its cache, performance, and other settings. In truth, there are other handy but hard-to-discover ways of configuring Firefox to behave according to your wishes.
Firefox inherits a number of hidden configuration interfaces from its Netscape ancestors, namely its 'about:' URIs (Uniform Resource Identifiers). For instance, in last April's Internet Tips column (under "Clear the Cache"), I wrote that unlike Internet Explorer, Firefox doesn't allow you to view the contents of its cached Web pages and related files. While it is true that you won't find a menu command or setting in the program's interface for that task, reader Fran Snyder, who contacted me via e-mail, notes that all you have to do is type about:cache into Firefox's address field and press <Enter> to view links to the contents of the browser's memory and disk caches.
So why would you ever want to peruse your Web browser's cache? The most obvious reason is that accessing the cache permits you to reopen the pages, images, and Flash animations you have viewed most recently, even when you aren't connected to the Internet. You can also save cached files to another spot on your hard disk or to removable storage.
Firefox's voluminous about:cache display doesn't make it easy, however--your best chance of finding a cached file is to press <Ctrl>-F to open the Firefox search bar, type a portion of the Web site's domain name, the file name or extension, or some other part of the address into the find field, and press <Enter>. For example, if you're looking for flash files, enter .swf. Or for images you saw on the New York Times' site, enter nytimes.com.
About:cache is just one of Firefox's hidden resources (you can see a complete list of these 'about:' URIs). Type about:about or just about: to see detailed information on your version of Firefox. Enter about:credits to view the names of the scores of developers who dedicated their free hours to creating and improving the browser, and type about:plugins to list all of the plug-ins currently installed. If you're sure you'll forget all of the above, no problem--just install MR Tech's About:About Firefox extension, which adds the tools as links to the browser's Help menu (see FIGURE 1
Config-uring It Out
The most useful--and dangerous--of the built-in URIs is about:config. Similar to Windows' Registry, the about:config page serves as an interface to the many boolean, integer, and string variables that control every aspect of Firefox's behavior. The biggest problem with about:config is that, like the Registry, it is mostly indecipherable to the average user. And again like the Registry, it lists only those settings that are currently set overtly--many other default settings don't appear simply because they don't need to.
Fortunately, an about:config FAQ page on the Mozilla Foundation's MozillaZine site lists everything you can do within about:config.
Lastly, if you use browsers other than Firefox, note that they offer similar hidden settings and tools. Wikipedia's handy "URI scheme" entry has tips not only for Firefox, but also for Internet Explorer and Opera.