opera = (navigator.userAgent.indexOf('Opera') >= 0)? true : false;
dom = (document.getElementById)? true : false;
ie4 = (document.all && !dom)? true : false;
nn4 = (document.layers)? true : false;

function getElement( elemId ) {

    if (dom)
        return document.getElementById(elemId);
    else
        if (ie4)
            return document.all[elemId];
        else
            if (nn4)
                return document.layers[elemId];
    return null;
}