createMouseOvers = function()
{
  var p = 0, d = document.images;
  prelImgs = new Array();
  for (var i = 0; i < d.length; i++)
  {
    var o = d[i];
    if (o.src.indexOf('_def.') != -1)
    {
      var s = o.src, l = s.length, e = s.substring(l-4,l);
      o.outSrc = s;
      o.overSrc = s.substring(0,l-8)+'_ovr'+e;
      o.onmouseover = function(){this.src = this.overSrc;}
      o.onmouseout = function(){this.src = this.outSrc;}
      prelImgs[p] = new Image();
      prelImgs[p].src = o.overSrc;
      p++;
    }
  }
};

createMouseOvers();