Center Div on div with jQuery

[javascript]
// Centers on screen
jQuery.fn.center = function (div) {
this.css("position", "absolute");

var position = div.position();
this.css("top", Math.max(0, ((div.height() – this.outerHeight()) / 2) + position.top) + "px");

this.css("left", Math.max(0, ((div.width() – this.outerWidth()) / 2) + position.left) + "px");
return this;
};

//use
$(‘#ajxload’).center($(‘#mapWrapper’)).show();
[/javascript]