attachOnload(function() {
  var tbody = document.getElementById('toolbox').getElementsByTagName('tbody');
  for (var x = 0; x < tbody.length; x++) {
    for (var y = 0; y < tbody[x].rows.length; y++) {
      tbody[x].rows[y].onmouseover = function() { this.className = "hover"; };
      tbody[x].rows[y].onmouseout = function() { this.className = ""; };
    }
  }
});