jQuery.preloadImages = function()
{
  for(var i = 0; i<arguments.length; i++)
  {
    jQuery("<img>").attr("src", arguments[i]);
  }
}

jQuery.fn.center = function()
{
    this.css("position", "absolute");
    this.css("top", ((($(window).height() - this.outerHeight()) / 2) + $(window).scrollTop()) + "px");
    this.css("left", ((($(window).width() - this.outerWidth()) / 2) + $(window).scrollLeft()) + "px");

    return this;
}