Centering a div vertically & horizontally using jQuery

Question

I am using this script to center my div horizontally and vertically.

When the page loads the div gets centered vertically, not horizontally until I resize the brows

Answer 1

based on @dimi's answer, works better with multiple elements

$(".className").each(
    function () {
       $( this ).css("position","absolute");
       $( this ).css("left","50%");
       $( this ).css("margin-left", - $( this ).outerWidth()/2 );
       $( this ).css("top","50%");
       $( this ).css("margin-top", - $( this ).outerHeight()/2 );
       return this;
    }
);