var url = "http://" + global_vhost + "/" + evt + "/" + width + "x" + height + "/" + filename;
var img = document.getElementById(element_id);
if (img != null) {
var url = "http://" + global_vhost + "/" + evt + "/" + width + "x" + height + "/" + filename;
var img = document.getElementById(element_id);
if (img != null) {