function popup(page, id,tw,th)
{
posx = (screen.width/2)-(tw/2);
posy = (screen.height/2)-(th/2);
features = "resizable=no,toolbar=no,status=no,menubar=no,scrollbars=no,width=" + tw + ",height=" + th + ",top=" + posy + ",left=" + posx;
window.open(page,id,features); 
void(0);
}