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;

     }

    }

   }

  }

 }

}