function highlight(node) {
    if (node.nodeType == 3) {
      var val = node.nodeValue;
      var pos = val.toLowerCase().indexOf(text);
      if (pos >= 0 && !jQuery(node.parentNode).hasClass(className)) {
        var span = document.createElement("span");
        span.className = className;
        span.appendChild(document.createTextNode(val.substr(pos, text.length)));
        node.parentNode.insertBefore(span, node.parentNode.insertBefore(
          document.createTextNode(val.substr(pos + text.length)),
          node.nextSibling));
        node.nodeValue = val.substr(0, pos);
      }
    }
    else if (!jQuery(node).is("button, select, textarea")) {
      jQuery.each(node.childNodes, function() {
        highlight(this);
      });
    }
  }
highlight a given string on a jquery object by wrapping it in
span elements with the given class name.