function setupRollovers() {
 if (!document.getElementsByTagName)
   return;
 var all_links = document.getElementsByTagName('a');
 for (var i = 0; i < all_links.length; i++) {
   var link = all_links[i];
   if (link.className &&
       (' ' + link.className + ' ').indexOf(' rollover ') != -1)
   {
     if (link.childNodes &&
         link.childNodes.length == 1 &&
         link.childNodes[0].nodeName.toLowerCase() == 'img') {
       link.onmouseover = mouseover;
       link.onmouseout = mouseout;
     }
   }
 }
}

function findTarget(e)
{
 /* Begin the DOM events part, which you */
 /* can ignore for now if it's confusing */
 var target;

 if (window.event && window.event.srcElement)
   target = window.event.srcElement;
 else if (e && e.target)
   target = e.target;
 if (!target)
   return null;

 while (target != document.body &&
     target.nodeName.toLowerCase() != 'a')
   target = target.parentNode;

 if (target.nodeName.toLowerCase() != 'a')
   return null;

 return target;
}

function mouseover(e) {
 var target = findTarget(e);
 if (!target) return;

 // the only child node of the a-tag in target will be an img-tag
 var img_tag = target.childNodes[0];

 // Take the "src", which names an image called "something.ext",
 // Make it point to "something_over.ext"
 // This is done with a regular expression
 img_tag.src = img_tag.src.replace(/(\.[^.]+)$/, '_over$1');
}

function mouseout(e) {
 var target = findTarget(e);
 if (!target) return;

 // the only child node of the a-tag in target will be an img-tag
 var img_tag = target.childNodes[0];

 // Take the "src", which names an image as "something_over.ext",
 // Make it point to "something.ext"
 // This is done with a regular expression
 img_tag.src = img_tag.src.replace(/_over(\.[^.]+)$/, '$1');
}

// When the page loads, set up the rollovers
window.onload = setupRollovers;