Object.extend(Array.prototype, {
  maxHeight: function() {
    var h_max=0;
    this.each(function(node){
      h = parseInt(node.getStyle('height')) || node.clientHeight;
      if (h > h_max) h_max=h;
    });
    this.invoke('setStyle',{height:h_max+'px'});
    return this;
  }
});