function open_category(catID, preffix){
    xmlHttp=GetXmlHttpObject();
    if (xmlHttp==null)
    {
        alert ("Browser does not support HTTP Request");
        return;
    }

    spantowrite = preffix+catID;

    var spanobj=gettrailobj(spantowrite);
    var imgobj=gettrailobj("imageof"+preffix+"_"+catID);
    var imgsource=imgobj.src;
    if(imgsource.match('2p')) {
        imgobj.src=imgsource.replace('2p','2m');
        var url='show_category_subs.php?catID='+catID;
        url=url+"&sid="+Math.random();
        xmlHttp.onreadystatechange=stateChanged;
        xmlHttp.open("GET",url,true);
        xmlHttp.send(null);
    } else {
        imgobj.src=imgsource.replace('2m','2p');
        spanobj.innerHTML="";
        return;
    }
}