Praise jeebus, mouse gestures are available for Firefox.

I did a search on the Firefox homepage for "gestures" and stumbled onto their "Extensions" concept.
Turns out there's all sorts of upgrades available, created by those with time to spare.
https://addons.update.mozilla.org/extensions/moreinfo.php?application=firefox&id=39&vid=810

I've been using Avant Browser for some time, which is a third-party upgrade for IE, but I've grown tired of IE's security flaws. I liked Firefox (fast, pretty, secure) but can't live without mouse gestures: to go Back, you hold down the right-mouse-button then press the LMB, to go Forward hold down the LMB and click the RMB. Doesn't sound like much, but I do a metric shit-ton of browsing every day and this is a massive improvement. Download and rejoice!

http://www.mozilla.org/products/firefox/

Or, if you don't want to switch to Firefox, give Avant Browser a shot:
http://www.avantbrowser.com/