Try to find some way to disable the MathML thing.
If you can't, since I don't think you are using any MathML code anyway, it could be enough to just change te DOCTYPE line to the correct:
Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">