Why is my site displaying differently In Firefox than in Safari?

I manage a website called ShareDen.com (http://shareden.com/home) and it looks the right way in Mozilla Firefox and it's totally completely discombobulated in Safari. I Haven't tested it in other broswer's (still in process) however my guess is it looks horrible in IE 8.

Could it be because I just add开发者_运维问答ed the CSS Sticky Footer to my site? This wasn't happening before. Please help!

Thank you in advanced!

Start fixing those errors and retry. I suspect that it has to do with those lot of misnested tags which made Safari mad. The w3 errors points them out.

By the way, a Content-Type of application/xhtml+xml is not recommendable. Use text/html. It's after all just HTML.