function openWindow(url,width,height) {

x = (640 - width)/2, y = (480 - height)/2;

if (screen) {

y = (screen.availHeight - height)/2;

x = (screen.availWidth - width)/2; }

if (screen.availWidth > 1800) { 

x = ((screen.availWidth/2) - width)/2; } 

window.open(url,'popup','width='+width+',height='+height+', screenX='+x+',screenY='+y+',top='+y+',left='+x);

}