function addEvent(obj, evType, fn){
 if (obj.addEventListener){
    obj.addEventListener(evType, fn, true);
    return true;
 } else if (obj.attachEvent){
    var r = obj.attachEvent("on"+evType, fn);
    return r;
 } else {
    return false;
 }
} 

addEvent(window, 'load', openURL);

function openURL() {
	document.getElementById('content-IS').onclick = function() {document.location='http://www.nuffic.nl/international-students';return false;}
	document.getElementById('content-IO').onclick = function() {document.location='http://www.nuffic.nl/international-organizations';return false;}
	document.getElementById('content-NS').onclick = function() {document.location='http://www.nuffic.nl/nederlandse-studenten';return false;}
	document.getElementById('content-NO').onclick = function() {document.location='http://www.nuffic.nl/nederlandse-organisaties';return false;}
}