function rollSetup() {
 /** string added to "on" state images */
 var post = "_o";

 /** fetch the image tag array from the DOM */
 var imgTags = document.getElementsByTagName("img");

 /** loop through the images for find appropriate preloads */
 for (i=0; i < imgTags.length; i++) {
  /** make sure there is a source defined */
  if (imgTags[i].src != '') {
   /** make sure the image tag has a class */
   tmpClass = imgTags[i].className;
   if (tmpClass) {
    /** match the image rollover class */  
    if (tmpClass.match("rollover")) {
     /** store the image source to the 'imgOut' attribute */    
     imgTags[i].imgOut = new Image();
     imgTags[i].imgOut.src = imgTags[i].src;
	
     /** pull apart the source string */
     srcLength = imgTags[i].src.length;

     srcName = imgTags[i].src.substr(0, srcLength-4);
     srcExt = imgTags[i].src.substr(srcLength-4, srcLength);

     /** store the image source to the 'imgOver' attribute */
     imgTags[i].imgOver = new Image();
     imgTags[i].imgOver.src = srcName + post + srcExt;

     /** set up the 'onmouseover' and 'onmouseout' event handlers */     
     imgTags[i].onmouseover = function() {
      this.src = this.imgOver.src;
     }
     imgTags[i].onmouseout = function() {
      this.src = this.imgOut.src;
     }
    }
   }
  }
 }
}