With all of the talk of the new push to support Firefox I was surprised to find out that WebParts have limitations when displayed in Firefox. When I first ran across this issue I began searching the web to see what was going on. I found responses in newsgroups and various blogs from the ASP.NET team that in fact WebParts do not work in Firefox and that they were unable to remedy this before release. So what happens when you run WebParts in Firefox? Well for one the ability to put the page in design mode and move WebParts around does not work. Then there is the issue of the drop down menu that normally appears in any mode (Close, Min, etc..). It becomes a series of hyperlinks in the WebPart title bar area. I hope in the future this does get resolved but I am sure in the short term we are just going to have to live with this. For you reference I have included links that talk about this subject.
ASP.NET 2.0 Webparts don’t support Firefox out of the box