Basically, you have a character encoding mismatch, which is causing a no parse mode declaration error.
Specifically the browser is seeing a funny character before the DOCTYPE, since the browser is assuming the wrong character encoding, which is causing it to completely miss the DOCTYPE declaration (thanks for the clarification David):
character "þ" not allowed in prolog
In XHTML the encoding declaration for your HTML header of utf-16 is
<meta http-equiv="Content-Type" content="text/html; charset=utf-16" />
Currently, in your HTML header you are declaring utf-8
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
You have a non UTF-8 character on line 129, so you cannot do this. Additionally, it doesn't match with your files encoding or what your server is claiming the file is.
In your CSS, you should declare the encoding too. This goes on the very first line, before anything else.
@charset "utf-16";