Most of my web developing has been for a corporate environment, where every browser was IE (or we could say - install IE!), but now I have to develop for the internet in general. Today I found that more issues are handled if you set your browserCaps in your web.config so that ASP.NET sees FF as a “Up Level” browser (and not something like Netscape 2.0!!). Granted that there are other CSS issues and formatting issues, but I found that the majority of issues clear up once ASP.net knows about (and Opera, et al)

Good browserCaps reference