function link_popup(link_tag, image_width, image_height){
		var min_width = 600;
		var min_height = 400;
		var window_width = Math.max(360 + image_width, min_width);
		var window_height = Math.max(60 + image_height, min_height);
		var x = Math.floor((screen.width) ? (screen.width - window_width)/2 : 0);
		var y = Math.floor((screen.height) ? (screen.height - window_height)/3 : 0);
		var url = link_tag.getAttribute('href');
		var target = link_tag.getAttribute('target') || '_blank';
		var features = 'location=0,statusbar=0,resizable=yes,scrollbars=1,menubar=0,width=' 
			+ window_width + ',height=' + window_height + ',top=' + y + 
			',left=' + x;
		var theWindow = window.open(url, target, features);
		if (theWindow && !theWindow.closed) {
			theWindow.focus();
			return theWindow;
		} else {
			return false;
		}
	}