Most likely cause is that you have a script above the doctype which throws IE into quirks mode and behaves more like ie5 than anything built this century. Always remove all content from above the doctype including comments.
(The 1.1xhtml doctype isn't suitable either unless you are doing content negotiation.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
(BTW links are not allowed.)