var W3CDOM = (document.createElement && document.getElementsByTagName);
var mouseOvers = new Array();
var mouseOuts = new Array();
window.onload = init;
function init()
{
     if (!W3CDOM) return;
     var nav = document.getElementById('thumbnails');
     var imgs = nav.getElementsByTagName('img');
     for (var i=0;i<imgs.length;i++)
     {
          imgs[i].onmouseover = mouseGoesOver;
          imgs[i].onmouseout = mouseGoesOut;
          var suffix = imgs[i].src.substring(imgs[i].src.lastIndexOf('.'));
          mouseOuts[i] = new Image();
          mouseOuts[i].src = imgs[i].src;
          mouseOvers[i] = new Image();
          mouseOvers[i].src = imgs[i].src.substring(0,imgs[i].src.lastIndexOf('.')) + "_omo" + suffix;
          imgs[i].number = i;
     }
}
function mouseGoesOver()
{
     oldsrc = document.getElementById('mainImage').src;
     document.getElementById('mainImage').src = mouseOvers[this.number].src;
}
function mouseGoesOut()
{
    document.getElementById('mainImage').src = oldsrc;
}