function setpos(W, H, L, T){
  var pos = ""
  if (L < 0)
    L = screen.width - W + L
  if (T < 0)
    T = screen.height - H + T
  if (T == "cen")
    T = (screen.height - H)/2
  if (L == "cen")
    L = (screen.width - W)/2 - 12
  if (L>0 & T>0)
    pos =  ",screenX=" + L + ",left=" + L	
                + ",screenY=" + T + ",top=" + T
  else
    pos = ""
  return pos
  }