function display(str) {
    if(str == '-- 选择申请学校 --') {
      document.search1.courses.className = "off";
    } 
	else {
      // insert AJAX code here
      var http_request = false;
      if(window.XMLHttpRequest) { // Mozilla, Safari, ....
		http_request = new XMLHttpRequest();
      } 
	  else if(window.ActiveXObject) { // IE
		try {
				http_request = new ActiveXObject("Msxml2.XMLHTTP");
			} 
			catch (e) {
				try {
					http_request = new ActiveXObject("Microsoft.XMLHTTP");
					} 
			catch (e) {}
		}
      }

      if (!http_request) {
        alert('Giving up :( Cannot create an XMLHTTP instance');
        return false;
      }
      
	  // 定義事件處理函數為 alterContents()
      http_request.onreadystatechange = function() { 
                                        alertContents(http_request); };

      if(str == '南洋理工大学') {
        url = 'http://sg.tickstudy.com/wp-content/themes/ticksg/ntu.xml';
      } 
	  if(str == '新加坡国立大学') {
        url = 'http://sg.tickstudy.com/wp-content/themes/ticksg/nus.xml';
      }
      http_request.open('GET', url, true);
      http_request.send(null);
    }
  }

  function alertContents(http_request) {
    if (http_request.readyState == 4) {
      if (http_request.status == 200) {
        var xmldoc = http_request.responseXML;
        var nodes = xmldoc.getElementsByTagName('course');
        var current = document.search1.courses;

        var anode, tnode;
        while(current.hasChildNodes()) {
          anode = current.firstChild;
          current.removeChild(anode);
        }

        for(var i=0; i<nodes.length; i++) {
          anode = document.createElement("option");
          anode.setAttribute("value", i);
          if(i == 0) 
            anode.setAttribute("selected", "1");
          current.appendChild(anode);
          tnode = document.createTextNode(nodes[i].firstChild.data);
          anode.appendChild(tnode);
        }

        document.search1.courses.className = "on";
      } 
	  else{
        alert('您还没有选择专业。请耐心等待专业列表出现然后重新选择.');
      }
    }
  }

document.execCommand("BackgroundImageCache", false, true);