if you are trying to set up Google AdSense then you will run into error with Firefox 3.6.x. Haven't tested with other versions so 3.5.x could be possible ok.
Here is how it looks when you load AdSense in Firefox and below is screenshot from Chrome where everything is working fine.
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| Broken layout and no option to submit form |
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| This is how it should look |
To summarize it. If you planning to play around with AdSense use Chrome or Internet Explorer instead of Firefox.
