I have the following script which grabs all images in a div with id "right" and attaches "_mo" (+ suffix) to them on mouseover. These images are navigation thumbs that each link to a page which has the full version of the image (see for instance this page). The following works fine:
var W3CDOM = (document.createElement && document.getElementsByTagName);

var mouseOvers = new Array();
var mouseOuts = new Array();

window.onload = init;

function init()
        if (!W3CDOM) return;
        var nav = document.getElementById('right');
        var imgs = nav.getElementsByTagName('img');
        for (var i=0;i<imgs.length;i++)
                imgs[i].onmouseover = mouseGoesOver;
                imgs[i].onmouseout = mouseGoesOut;
                var suffix = imgs[i].src.substring(imgs[i].src.lastIndexOf('.'));
                mouseOuts[i] = new Image();
                mouseOuts[i].src = imgs[i].src;
                mouseOvers[i] = new Image();
                mouseOvers[i].src = imgs[i].src.substring(0,imgs[i].src.lastIndexOf('.')) + "_mo" + suffix;
                imgs[i].number = i;

function mouseGoesOver()
        this.src = mouseOvers[this.number].src;

function mouseGoesOut()
        this.src = mouseOuts[this.number].src;
However, I would like to extend it so that if a user is on a page that corresponds to the "active" thumb, that thumbnail-image has the "_mo" attached by default. I understand I'd have to give the "active" thumbnail an id of, say, "current" and then use the DOM to access it -- but that's where the trouble starts...

Thanks for any help!