Validate and clean up your xhtml first - there are some major problems with it. For starters, you have 2 different Doctype declarations in your code (and 2 <html> tags!).
Never try to validate CSS before you validate your (x)html.
Now the validation results for your xhtml are more reliable ...
Move the stylesheet that's around line #93 in your source into the head section. You can't have a stylesheet in the body of the page. Give a type="text/css" while you're at it.
Now the validation results for your xhtml are more reliable ...
Move the stylesheet that's around line #93 in your source into the head section. You can't have a stylesheet in the body of the page. Give a type="text/css" while you're at it.