Firefox: If you regularly tweak entries in Firefox's
about:config menu (as we often do), you've probably stumbled upon preferences that look interesting but you aren't sure how to use them. What's That Preference will tell you what they are.
You may not realise it, but Mozilla actually has loads of information about the preferences in
about:config over at the MozillaZine Wiki. What's That Preference is a simple Firefox add-on that lets you look up any preference, from the
about:config window, on the wiki. Just install it, and when you see something interesting in about:config, right-click on it and hit "MozillaZine reference" to see what it does.
What's That Preference is a free download, works wherever Firefox does.