function createXHRobj() {
    var xmlhttp = false
    try {
        xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
    } catch (e) {
        try {
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        } catch (E) {
            xmlhttp = false;
        }
    }
    if (!xmlhttp && typeof XMLHttpRequest!='undefined') {
	    try {
		    xmlhttp = new XMLHttpRequest();
	    } catch (e) {
		    xmlhttp=false;
	    }
    }
    if (!xmlhttp && window.createRequest) {
	    try {
		    xmlhttp = window.createRequest();
	    } catch (e) {
		    xmlhttp=false;
	    }
    }
    return xmlhttp    
};

function showSubjects(height,thisID){

	var xmlhttp=false;
	xmlhttp = createXHRobj()
	if (xmlhttp) {	  
		var rd14 = document.getElementById("rad14")
		var level
		if (!rd14.checked){
			level = 16;
		}else{
			level = 14;
		}		
		var s = document.getElementById(height+'List'+thisID);
		var img = document.getElementById(height+'Img'+thisID);
		if (s.innerHTML == ''){
			s.innerHTML = 'Loading...<br />'
	
			//open xmlhttp request
			xmlhttp.open("GET", "getSubjects.aspx?level="+level+"&height="+height+"&ID="+thisID,true);
			xmlhttp.onreadystatechange=function() {
				if (xmlhttp.readyState==4) {
				//if readystate 4 then info is loaded from getSubjects
					//hide all info of a set height
					changeLevel(height);
					//populate span s with response HTML
					var strResponse = xmlhttp.responseText;
					s.innerHTML = strResponse;
					img.src = "images/AGminus.gif";
				}
			}
			xmlhttp.send(null)
		}else{
			s.innerHTML = '';
			img.src = "images/AGplus.gif";
		}
	}
	return !xmlhttp;
}