[Lea Verou]

I want to preload some images.
I used this javascript code:

window.onload = function preload_tabimages() 
    {
        //preloading images
        var gk_tab = new Image();
        gk_tab.src = "$vboptions[bburl]/newera/karteles/gk.gif";
        var t_tab = new Image();
        gk_tab.src = "$vboptions[bburl]/newera/karteles/t.gif";
        var ets_tab = new Image();
        gk_tab.src = "$vboptions[bburl]/newera/karteles/ets.gif";
        var sx_tab = new Image();
        gk_tab.src = "$vboptions[bburl]/newera/karteles/sx.gif";
        var s_tab = new Image();
        gk_tab.src = "$vboptions[bburl]/newera/karteles/s.gif";
    }

but it doesn't seem to work... Any ideas?
Thanks in advance!