function popup (link, window_name, width, height)
{
  //if (!window.focus) return true;
  var href;
  if (typeof(link) == 'string')
    href=link;
  else
    href=link.href;
    
  var page_width = screen.width ;
  var width = page_width*0.75 ;
  var height = width*0.75
  var screen_x = page_width*0.15 ;
  var screen_y = page_width*0.10 ;

  if (!width)
    width = page_width*0.75 ;

  if (!height)
    height = width*0.75
  
  var new_window = window.open(href, window_name, 'width='+width
         +',height='+height+',screenX='+screen_x+',screenY='+screen_y+',scrollbars=1,resizable=1');
  if (window.focus) new_window.focus() ;
  return false;
}