var preimgon = new Array(), preimgoff = new Image();
var xparobj = document.getElementsByName("roll");
var acount;

acount=xparobj.length;

function rollon(){
  xsubobj=this.getElementsByTagName("img")[0];
  preimgoff.src=xsubobj.src;
  xsubobj.src=preimgon[this.accessKey].src;
  
}

function rolloff(){
  xsubobj=this.getElementsByTagName("img")[0];
  if (preimgoff.complete)
    xsubobj.src=preimgoff.src;
}


  if (acount>=0) {
    for (i=0; i<acount; i++) {
      preimgon[i]=new Image();
      xsubobj = xparobj[i].getElementsByTagName("img")[0];

      str=xsubobj.src;
      preimgon[i].src = str.substr(0,(str.length-4)) + "_f2" + str.substr((str.length-4),4);
      xparobj[i].accessKey=i;
      xparobj[i].onmouseover=rollon;
      xparobj[i].onmouseout=rolloff;
    }
  }