Working on a perl-based CMS, I get bitten by client-side caching a lot.  I make a change, and even though I'm in admin mode or whatever, Firefox will not go and get new data for me.

To get around this, I installed the Clear Cache plug-in for Firefox.  I get a button right on top of the toolbar to clear the cache, instead of digging through the Preferences dialog box to do it.  If I wasn't so lazy, I could probably also assign a bindkey to do it as well.