// JavaScript Document

var myLayer = "air_image1";
var myLayer1 = "ext_image1";
var myLayer2 = "int_image1";

function getStyleObject(objectId) {
	if(document.getElementById && document.getElementById(objectId)) return document.getElementById(objectId).style;
	else if (document.layers && document.layers[objectId]) return document.layers[objectId];
	else return false;
}

function hideLayer(which) {
	// hide the form layer
	var Object = getStyleObject( which );
	if( Object ) {
		Object.visibility = "hidden";
	}
}

function showLayer(which,num) {
	if (num == null || num == "") {
		hideLayer(myLayer);
		myLayer = which;
	} else if (num == 1) {
		hideLayer(myLayer1);
		myLayer1 = which;
	} else if (num == 2) {
		hideLayer(myLayer2);
		myLayer2 = which;
	}
	// show the form layer
	var Object = getStyleObject( which );
	if( Object ) {
		Object.visibility = "visible";
	}
}