function open_new_window(url)
{ 
winLeft = (screen.width-800)/2; 
winTop = (screen.height-720)/2; 
if (screen.width<850 || screen.height<650) new_window = window.open(url,'my_window','scrollbars=1,toolbar=0,menubar=0,resizable=0,dependent=0,status=0,width=800,height=630,left='+winLeft+',top='+winTop);
else new_window = window.open(url,'my_window','scrollbars=0,toolbar=0,menubar=0,resizable=0,dependent=0,status=0,width=800,height=630,left='+winLeft+',top='+winTop);
}