you do seem to have a class for a link which is yr current page, but you can do the same thing by putting the links in a <span> rather than a list item.. so, replace the <li>'s with <span> and <span class="current"> for each page where the link is to the page you are currently on?
like this? how does that look?.. just paste what I've done next to your div, and comment out your div for the moment by putting <!-- at the start of it and --> at the end of it.
<div id="left">
<div id="navbar">
<span><a href="index.html" title="Zurück zur Startseite">home</a></span>
<span><a href="graphics.html" title="graphics">graphics</a></span>
<span class="current"><a href="music.html" title="music">music</a></span>
<span><a href="reservierung.html" title="Reservierung">films</a></span>
<span><a href="contact.html" title="contact">contact</a></span>
</div>
</div>