var _preview_box_original;

function ThumbGrid(thumbsid, previewid) {
  var thumbs = document.getElementById(thumbsid);
  var preview = document.getElementById(previewid);
  _preview_box_original = preview.innerHTML;
  
  for (var i=0; i<thumbs.childNodes.length; i++) {
    var a = thumbs.childNodes.item(i);
    if (a.nodeName.toLowerCase() == "a") {
      a.onmouseover = function() {
        preview.innerHTML = "<img src='" + this.getElementsByTagName("IMG")[0].src.replace(/thumbs/, "preview") + "' />";
        preview.style.background = "white";
        preview.style.display = "block";
      }
      
      a.onmouseout = function() {
        preview.innerHTML = _preview_box_original;
        preview.setAttribute('style', '');
        preview.style.display = "none";
      }
    }
  }

}