function prepareLinks() {
	if (!document.getElementsByTagName) return false; /*browser object detection*/
	var links = document.getElementsByTagName("a");
	for (var i=0; i<links.length; i++) {
		if (links[i].getAttribute("class") == "popup" || links[i].className == "popup") {
			links[i].onclick = function() {
				popUp(this.getAttribute("href"));
				return false;
				
			}
		}
	}
}

function popUp(imageURL) {

	var w = screen.width; 
	var h = screen.width; 
	var my_position = "width="+w+",height="+h;
	
	var leftPos = (screen.width) ? (screen.width-w)/2 : 0;/**/
	var topPos = (screen.height) ? (screen.height-h)/2 : 0;/**/
	var my_features = "resizable=1,toolbar=0,location=0,statusbar=0,menubar=0,scrollbars=0,"+"top="+topPos+",left="+leftPos +","+my_position;
  	newWindow = window.open(imageURL,"PopUp",my_features);
}

function addLoadEvent(func) { 
	//thx Simon Williams
	var oldonload = window.onload;
	if (typeof window.onload != 'function') {
		window.onload = func;
	} else {
		window.onload = function() {
			oldonload();
			func();
		}
	}
}

addLoadEvent(prepareLinks);