CKEditor adds the unwanted code "html contenteditable=true".
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html contenteditable="true" lang="en" xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">

Re: CKEditor 3.3 adds unwanted "contenteditable=true"
http://dev.fckeditor.net/ticket/5790