function showHide(shID) {
   if (document.getElementById(shID)) {
      if (document.getElementById(shID+'-show').style.display != 'none') {
         document.getElementById(shID+'-show').style.display = 'none';
         document.getElementById(shID).style.display = 'block';
      }
      else {
         document.getElementById(shID+'-show').style.display = 'inline';
         document.getElementById(shID).style.display = 'none';
      }
   }
}




    if (document.images)
    {
      preload_image_object = new Image();
      // set image url
      image_url = new Array();
      image_url[0] = "../images/nav-waterb.gif";
      image_url[1] = "../images/nav-waterb-over.gif";
      image_url[2] = "../images/nav-climateb.gif";
      image_url[3] = "../images/nav-climateb-over.gif";
      image_url[4] = "../images/nav-foodb.gif";
      image_url[5] = "../images/nav-foodb-over.gif";
      image_url[6] = "../images/nav-healthb.gif";
      image_url[7] = "../images/nav-healthb-over.gif";
       var i = 0;
       for(i=0; i<=3; i++) 
         preload_image_object.src = image_url[i];
    }