Try killing all the whitespace before the DOCTYPE.
EDIT: There is an <feff> character which is a Unicode BOM signature at the start of the file. Since you may not have a text editor that can actually see that, try deleting the entire first line and paste over it with
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
And do NOT save the file with a BOM unicode signature. If this doesn't work, try a different text editor altogether.
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