It's not because I wrote it (ok, yes, it's because I wrote it) but if you ever need a "clean" browser, without cookies etc for tests, you can do worse than using my Devicenzo like this:
rm -f ~/.config/ralsina/devicenzo.conf curl https://devicenzo.googlecode.com/svn/trunk/devicenzo.py | python
The first line removes all configuration, cookies, etc, you may have and the second one downloads the latest version (don't worry, it takes about 2 seconds) and launches it.
And voilá, a completely fresh out-of-the-box, webkit-based browser, with no previous history, cookies, or configuration, fairly feature-complete.
this requires you having python and PyQt already installed (which is why devicenzo itself is so tiny)