function popup(file,name,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;
}

var newWindow = window.open(file,name,'width='+width+',height='+height+',screenX='+x+',screenY='+y+',top='+y+',left='+x+',scrollbars=no,toolbar=no,menubar=no,status=no');


}