Firefox is my favourite browser and rapidly gaining popularity too and it would help to make websites more compatible with it.
Did you notice a small button in the firefox navigation toolbar that helps you Report Broken Websites in Firefox.
If you do not see it, you can right click on the toolbar, Select Customize and find that icon. Then you can drag and drop it into yor navigation toolbar. Known as Firefox Reporter, the tool is designed to make it easy for users to send details about sites that do not work well with Firefox. I suppose this is a Firefox 1.5 feature since I never saw it before.
You can also use the ‘Report Broken Web Site‘ in the Help menu to fill out a problem report with all the necessary details. Check out the Mozilla Reporter where these error reports are collected and fixed by professional developers. So help find and report bugs to Mozilla and make Firefox a better browser.