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.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…