function mouseOver()
{
   // handle browser differences
   var srcEl = event.srcElement? event.srcElement : event.target;    

   // change the src of the image from "_off" to "_over"
   srcEl.src = srcEl.src.replace("_off", "_over");
}

function mouseOut()
{
   // handle browser differences
   var srcEl = event.srcElement? event.srcElement : event.target;    
   
   // change the src of the image from "_off" to "_over"
   srcEl.src = srcEl.src.replace("_over", "_off");
}

function initRollovers()
{
   // loop through the images in the document and search for 
   // images that contain "_rollover" in the img NAME property
   for (i=0; i<document.images.length; i++)
   {
      var img = document.images[i];
      if (img.name.indexOf("_rollover") != -1)
      {
         // if we find an image with "_rollover" in the name property

         // preload the _over image
         // not strictly necessary, but should increase responsiveness
         var imgOver = new Image();
         imgOver.src = img.src.replace("_off", "_over");
         
         // assign event handlers to the image
         img.onmouseover = mouseOver;
         img.onmouseout  = mouseOut;
      }
   }
}