Hey guys,

I'm relatively new to the forum so forgive me if this is a naive question or something that's been asked a billion times before. This is fairly straightforward, so I'm sure it's come up here before... However, I ran a search and didn't find anything.

Basically, I can't get Youtube video embeds to work in HTML5 documents.

If I just run a normal (X)HTML document, starting with this formatting:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">

I can run a youtube embed like, <iframe width="420" height="315" src="//www.youtube.com/embed/oUjUTG3hwyQ" frameborder="0" allowfullscreen></iframe> and it will show perfectly.

But if I use the HTML5 formatting:

<!DOCTYPE html>
<html lang="en">
<html>
<head><title>html5 site</title>
<meta charset= "UTF-8">

I won't get a video. Instead, in Chrome, it will say "the file or directory cannot be found." In internet explorer, it will say "page cannot be displayed."

What's going on here?