If you take a look at the source, it should be somewhat obvious.
All the code at the top stays there; you can change the below, or just add your code in after it.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
Then, the next part stays there, and you can add anything else you want just before this: