function toggleLayer( whichLayer )
{
    var elem, vis;
    elem = getRef(whichLayer);
    vis = elem.style;
    // if the style.display value is blank we try to figure it out here
    if (vis.display == '' && elem.offsetWidth != undefined && elem.offsetHeight != undefined)
        vis.display = (elem.offsetWidth != 0 && elem.offsetHeight != 0) ? 'block' : 'none';
    vis.display = (vis.display == '' || vis.display == 'block') ? 'none' : 'block';
}
function getRef(whichLayer) {
    var elem; 
    if( document.getElementById ) // this is the way the standards work
        elem = document.getElementById( whichLayer ); 
    else if( document.all ) // this is the way old msie versions work
        elem = document.all[whichLayer];
    else if( document.layers ) // this is the way nn4 works
        elem = document.layers[whichLayer];
    return elem;
}