function imgON(imgName)
{
   if (document.images)
   {
   imgChange = this.document[imgName].src
   imgChange = imgChange.replace("_off","_on");
   this.document[imgName].src = imgChange;
   }
}

function imgOFF(imgName)
{
   if (document.images)
   {
   imgChange = this.document[imgName].src
   imgChange = imgChange.replace("_on","_off");
   this.document[imgName].src = imgChange;
   }
}