Sådan ?
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"
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<meta http-equiv="content-type" content="text/html; charset=iso-8859-1">
<title>Ingen titel</title>
<script type="text/javascript">
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function layhideandshow(showid){
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laycheck2=laycheck.getElementsByTagName("div");
for(runit=0;runit<laycheck2.length;runit++){
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</head>
<body>
<div id="Menuboks" style="float:left;width:150px;height:100%;>
<ul>
<li><a href="java script: layhideandshow(1);"
onclick="layhideandshow(1);">Forsiden</a></li>
<li><a href="java script: layhideandshow(2);">Side1</a></li>
<li><a href="java script: layhideandshow(3);">Side2</a></li>
<li><a href="java script: layhideandshow(4);">Side3</a></li>
<li><a href="java script: layhideandshow(5);">Side4</a></li>
</ul>
</div>
<div id="divlayers" style="float:right;width:600px;">
<div id="layer1" class="Centerboks">Forside</div>
<div id="layer2" class="Centerboks" style="display:none;">Dit layer nr 1</div>
<div id="layer3" class="Centerboks" style="display:none;">Dit layer nr 2</div>
<div id="layer4" class="Centerboks" style="display:none;">Dit layer nr 3</div>
<div id="layer5" class="Centerboks" style="display:none;">Dit layer nr 4</div>
</div>
</div>
</body></html>