Most of the problems I have had with browsers other than ie is when webmasters cant write javascript's, so some menues dont work as intended...
I know that ie accept some errors in the javascript-code(I wont even begin talk about what think about that). Most other browsers dont.

I do it the hard way, I write the webmaster a email telling them about the errors...
I would like to fire them from their work - but unfortunately its not in my powers...

/Fredrik