var topNavNames;
function setHeaders(arrayHead) {
	topNavNames = arrayHead;
	preload();
}

var navImgDir = "images/";
var onImg = new Array();
var offImg = new Array();

function preload() {
	var imgName, imgHLName, refName;
	if (document.images) {       //if image object is available
		for (var i = 0; i < topNavNames.length; i++) {
		  	refName = topNavNames[i];
			imgName = navImgDir + refName + "_off.gif";
			imgHLName = navImgDir + refName + "_on.gif";
			onImg[refName] = new Image();
			offImg[refName] = new Image();
			onImg[refName].src = imgHLName;
			offImg[refName].src = imgName;
		}
	}	
}

function imageOn(name) {
   if (document.images) {
    document.images[name].src = onImg[name].src
   }
}

function imageOff(name) {
   if (document.images) {
    document.images[name].src = offImg[name].src
   }
}