writing html content to div tag with javascript

the code:
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function WriteLayer(ID,parentID,URL) {
if (document.layers) {
var oLayer;
if(parentID){
oLayer = eval('document.' + parentID + '.document.' + ID + '.document');
}else{
oLayer = document.layers[ID].document;
}
oLayer.open();
oLayer.write(URL);
oLayer.close();
}
else if (parseInt(navigator.appVersion)>=5&&navigator.
appName=="Netscape") {
document.getElementById(ID).innerHTML = URL;
}
else if (document.all) document.all[ID].innerHTML = URL
}
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im using like this:

<a href="javascript:WriteLayer('ctd',null,'testing')">blablabla</a>
<div class='ctd'></div>

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may be a spelling problem, but what can i do to put html url (testing.html for example)
and not the entire code into a tag?
thanks for any help