$
(
    function()
    {
        var backgroundheight = 2000;

        offset = Math.round(Math.floor(Math.random()* 2001));

        function scrollbackground()
        {
            offset = (offset < 1) ? offset + (backgroundheight - 1) : offset - 1;

            $('#BgEffect').css("background-position", "50% " + offset + "px");

            setTimeout(function(){scrollbackground();}, 100);
        }

    	scrollbackground();
    }
);