var popUpWin=0;
function popUpWindow(theURL,winName,features)
{
  if(popUpWin)
  {
    if(!popUpWin.closed) popUpWin.close();
  }
  popUpWin = open(theURL,winName,features);
}

function roll_over(img_name, img_src)
   {
   document[img_name].src = img_src;
   }