own dropdown menu doesnt work in WordPress

Hello all,

Ive been trying to integrate wordpress in my own site layout which i have been using for a while now.

My site is http://www.focasa.nl

If you check the menu, eg “modelfotografie”, you will see a dropdown menu pops up.
I have tried a lot of tutorials on how to integrate WP into your own site layout. Seems like everything can/will be working with the exception of the dropdownmenu.

The code used for this dropdownmenu is

<nav class="main-menu">
  <ul class="sf-menu">
    <li class="current"><a href="http://www.focasa.nl/overmij.html"><em>over mij</em><strong></strong></a>
				</li>
				<li><a href="http://www.focasa.nl/modellen.html"><em>modelfotografie</em><strong></strong></a><ul>
						<li><a href="http://www.focasa.nl/modellen.html">modelfotografie</a></li>
						<li><a href="http://www.focasa.nl/TFshoot.html">shoots op TF* basis</a></li>
 				</ul>
				</li>
				<li><a href="http://www.focasa.nl/familie.html"><em>familieshoots</em><strong></strong></a></li>
				<li><a href="http://www.focasa.nl/zwangerschap.html"><em>zwangerschappen</em><strong></strong></a></li>
				<li><a href="http://www.focasa.nl/bruiloft.html"><em>bruiloften</em><strong></strong></a></li>
				<li><a href="http://www.focasa.nl/portfolio.html"><em>portfolio</em><strong></strong></a></li>
				<li class="last"><a href="http://www.focasa.nl/contact.html"><em>contact</em><strong></strong></a></li>
			</ul>
			<div class="clear"></div>
		</nav>

the scripts are linked too as :

<link rel="stylesheet" href="http://www.focasa.nl/css/style.css">
<script src="http://www.focasa.nl/js/jquery-1.7.1.min.js"></script>
<script src="http://www.focasa.nl/js/script.js"></script>

Strange thing: if I copy out the header and copy it to a new blank file in Dreamweaver, save it as HTML, the dropdownmenu will be working.
If I copy the exact same thing into WP’s header.php and save it, it doesnt work….

I know this post my look like a mess, but I hope someone can help me out here.
Im a noob in PHP language. 🙁

Thanx a million !!!