function getGETParameter(){
HTTP_GET_VARS=new Array();
strGET=decodeURI(document.location.search.substr(1,document.location.search.length));
if(strGET!='')
    {
    gArr=strGET.split('&');
    for(i=0;i<gArr.length;++i)
        {
        v='';vArr=gArr[i].split('=');
        if(vArr.length>1){v=vArr[1];}
        HTTP_GET_VARS[unescape(vArr[0])]=unescape(v);
        }
    }

function GET(v)
{
if(!HTTP_GET_VARS[v]){return 'undefined';}
return HTTP_GET_VARS[v];
}

var allSelects = document.getElementById("thema");
var mySelect = allSelects[0]; // reicht aus, wenn es nur ein Select-Feld gibt

if (allSelects.length > 1) {
    // es gibt (leider) doch mehrere Select-Felder
    for (var i=0; i < allSelects.length; i++) {
		if (document.getElementById("thema").options[i].text == GET('seminar')) {
			document.getElementById("thema").options[i].selected='selected';
		}
    }
}

}