Testing in Firefox 3.6 (testing platform?)

Question

1.Do you have any ideas on how to test websites in firefox 3.6 if I have win7 and ff6 installed? I've tried to install 3.6 and alongside with ff 6 but it gets all messy. Is there something like Ie tester for fire fox 3.6? Adobe lab-browser sucks because it's not "live".
2.How do you test your sites? (apart from the mentioned above)
3.If any one has ff 3.6 (and fire bug) could check this site and tell me what's wrong? http://dissbike.pl/

Thanks!