That’s curious. I often insert videos using this technique in a SS blog and I could paste your code straight into a test page without issues.
403//<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<h1>Forbidden</h1> <p>You don't have permission to access /admin/EditForm on this server.</p>
<hr> <address>Apache/2.2.0 (Fedora) Server at m.imaginationlab.nl Port 80</address>