Simulate position:fixed with bottom with jQuery

[javascript]
var genuineBottom = parseInt($("#alertwindow-‘.$view->getParam("uniqid").’").css("bottom").slice(0,-2),10);
if (genuineBottom == undefined || genuineBottom == NaN)
{
genuineBottom = 0;
}

$(window).scroll(function() {
offset = $($("#alertwindow-‘.$view->getParam("uniqid").’")).offset();
var newTop = $(window).height() – $("#alertwindow-‘.$view->getParam("uniqid").’").height() + $(window).scrollTop() – genuineBottom;
$("#alertwindow-‘.$view->getParam("uniqid").’").css("top", newTop + "px");
});
[/javascript]