Firefox is a bad browser? 
I'm using 6.0 Beta right now and I love it and haven't had any problems here, so far. Just upgraded early this week and haven't tried everything (such as the new live chess) so I can't say it doesn't have issues.
Here is an older topic (from March-April) on IE 9.
posting doesn't work with internet explorer 9. I can post once after that nothing happens when I click the submit button. So I have to use firefox which is a bad browser but it works all the time.
any plans to make posting work with IE9.