function openWindow(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('popup.html','vlan','width='+width+',height='+height+',screenX='+x+',screenY='+y+',top='+y+',left='+x);
}