function findElement(n,ly) {
	if (browserVers < 4)		return document[n];
	var curDoc = ly ? ly.document : document;
	var elem = curDoc[n];
	if (!elem) {
		for (var i=0;i<curDoc.layers.length;i++) {
			elem = findElement(n,curDoc.layers[i]);
			if (elem) return elem;
		}
	}
	return elem;
}

function changeImages() {
    if (document.layers) {
	    img = findElement(mapid,0);
    }
    else
    {
        img = document.images['mapid'];
     }
    if (changeImages.arguments.length == 0)
    {
     	img.src =  document.getElementById('mapdefaultid').value
    }
    else
    {
    
        img.src = changeImages.arguments[0];
    }
}