I copied the code from the box, pasted into my htm...

I copied the code from the box, pasted into my html and it gives me one error reading after another. First it said the doctype html was not closed, then when I fixed it, it started to tell me "content not allowed in prolog". Having no html experience whatsoever, I don't even know what that means. I'm in the updated template, not classic, and the "expand widgets" box is checked