Well, I always complained about the threading problems in Firefox (Windows XP). For example Firefox won’t let you use any mouse gestures (e.g. switch to next tab) while it is loading plugins or just web-content in the recent tab. I guess the plugins just have lower priority than the render engine. But you can still use the keyboard shortcuts to switch the tabs at all times.
In Mac OS X I had the problem that some browsers don’t support mouse gestures at all.
So I had to find some application for Global Mouse Gestures on both systems.
Lets start with Windows XP.
StrokeIt (0.9.5) is some great Freeware tool that lets you define global and local (for individual window classes) mouse gestures for all your needs. It even offers gesture feedbacks like line-drawings in individual colors. Since the global keyboard and mouse events have almost the highest priority in Windows XP it is much faster than any plugin for Firefox like Mouse Gestures 1.5.1 or All-in-One Gestures 0.17.4.
Now for Mac OS X ( PPC and Intel Mac).
CocoaSuite (universal binary), formerly know as CocoaGestures, was originally Freeware but the project was integrated into the new Payware CocoaSuite. You can still download the old CocoaGestures 1.2 from MacUpdate but I guess it only works on PPC. So CocoaSuite works only on for Cocoa apps and costs like “US$14.95” recently. It works pretty well and 30–day trial is OK for AppZapper if you know what I mean.