There’s a bunch of different tools, add-ons and plugins that I find handy for web and RIA development. However, in terms of sheer usefulness, I would have to say that one stands out above all others: The Firefox Clear Cache Button Add-on:
The Clear Cache Button does exactly as the name suggests, and it does nothing else. It doesn’t clear your cookies, history or any private data at all. It just clears the browser cache. And because it’s a toolbar button, it’s right there. You don’t need to click through a barrage of menus, dialogs and radio buttons.
Browsers are quirky in the way they cache certain types of content. Sometimes images, JavaScript files, CSS files or even SWFs may get pulled from browser cache, without the browser even re-requesting them to see if there is an upated version (which of course, has just been updated). Now browsers do provide a fairly standard way to clear cache (via menus), but over the years the default options have come to include clearing your history and cookies – things that improve productivity, and you don’t really want to lose. You can selectively disable things you don’t wish to clear, but it’s time-consuming.
I swear I can see the little broom icon on the button in my toolbar fading, as a result of its frequent use.