function setRollover(){
 var divs = document.getElementsByTagName("div");
 var imgs = document.getElementsByTagName("img");
 var i;
 var regex = new RegExp("imgs|imgs_r|imgs_l","i");
 
 for(i=0;i<divs.length;i++){
  if(divs[i].className.toLowerCase() == "category_item"){
   divs[i].onmouseover=mouseOver;
   divs[i].onmouseout=mouseOut;
  }
 }
 
 for(i=0;i<imgs.length;i++){
  if(regex.test(imgs[i].className)){
   imgs[i].onmouseover=mouseOver;
   imgs[i].onmouseout=mouseOut;
  }  
 }
}

function mouseOver(){
  this.className=this.className + " on";
}

function mouseOut(){
 this.className=this.className.replace(" on","");
}

window.onload = setRollover;