For the beginning, you should code according to the standards. Your Doctype
should be placed above
the HTML tag. In order to be sure for a crossbrowser compatibility, you'd better use at least a HTML strict DTD:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
And coding according to the strict DTD exigences.
On the other hand, you can not nest a HTML document inside another HTML document like that:
You can not have more then a single HTML, a single HEAD and a single BODY tag within the same document.