function _HpbImgSwap(imgName, imgSrc)
{
  var appVer=parseInt(navigator.appVersion);
  var isNC=false,isN6=false,isIE=false;
  if (document.all && appVer >= 4) isIE=true; else
    if (document.getElementById && appVer > 4) isN6=true; else
      if (document.layers && appVer >= 4) isNC=true;
  if (isNC||isN6||isIE)
  {
    if (document.images)
    {
      var img = document.images[imgName];
      if (!img) img = _HpbImgFind(document, imgName);
      if (img) img.src = imgSrc;
    }
  }
}

function _HpbImgFind(doc, imgName)
{
  for (var i=0; i < doc.layers.length; i++)
  {
    var img = doc.layers[i].document.images[imgName];
    if (!img) img = _HpbImgFind(doc.layers[i], imgName);
    if (img) return img;
  }
  return null;
}

function _setCaption(id, text) {
	document.all[id].innerHTML=text;
}


current = 1;
largeNumber = 1;
text = "";
propID = "";
imagesLoaded = false;


var capArray = new Array();
	
	capArray[1] = "The first caption ....";


if (document.images) {


  var thumbImg1 = new Image();
  var thumbImg2 = new Image();
  var thumbImg3 = new Image();
  var thumbImg4 = new Image();
  var thumbImg5 = new Image();
  var thumbImg6 = new Image();
  var thumbImg7 = new Image();
  var thumbImg8 = new Image();
  var thumbImg9 = new Image();
  var thumbImg10 = new Image();
  var thumbImg11 = new Image();
  var thumbImg12 = new Image();
  var thumbImg13 = new Image();
  var thumbImg14 = new Image();
  var thumbImg15 = new Image();
  var thumbImg16 = new Image();
  var thumbImg17 = new Image();
  var thumbImg18 = new Image();
  var thumbImg19 = new Image();
  var thumbImg20 = new Image();
  var thumbImg21 = new Image();
  var thumbImg22 = new Image();
  var thumbImg23 = new Image();
  var thumbImg24 = new Image();
  var thumbImg25 = new Image();
  var thumbImg26 = new Image();
  var thumbImg27 = new Image();
  var thumbImg28 = new Image();




  var imagecaption1 = "The first caption ....";
  var imagecaption2 = "The second caption ...";

	var rgt_on = new Image();
	var rgt_off = new Image();

	var lft_on = new Image();
	var lft_off = new Image();
}


function preloadImages() {
	if (document.images) {

		//arrow buttons
		rgt_on.src  ="../uparrow.jpg";
		rgt_off.src ="../uparrow.jpg";
		lft_on.src  ="../downarrow.jpg";
		lft_off.src ="../downarrow.jpg";

		imagesLoaded = true;
	}
}

<!-- imgFunctions.js -->


function setThumbnail(thumbLocation, thumbImage) {
	if (imagesLoaded == true) {
		imgName = ("thumb" + thumbLocation);
		if (document.images) {
			document[imgName].src = eval("thumbImg" + thumbImage + ".src");
		}
	}
}

function setCaption(number) {
	text = capArray[number];
	layerWrite('caption',text);
}

function layerWrite(id, text) {
	document.getElementById(id).innerHTML = text;
}


<!-- setting large image -->
function setLargeImage() {
	largeImageWindow = window.open(largeImageArray[largeNumber],'largeImage','width=550,height=369,left=600,top=100,screenX=600,screenY=100');
	//alert(largeNumber);
}


function clickdown() {
	if (current + 2 < thumbCount) {
		current = current + 1;
		setAllThumbs(current)
	}
	// setArrows();
}

function clickup() {
	if (current > 1) {
		current = current - 1;
		setAllThumbs(current)
	}
	// setArrows();
}


function setSlide(thumbLocation) {
	slideNumber = current + thumbLocation - 1
	if (document.images) {
		document["slide"].src = eval("slideURL" + slideNumber);
		largeNumber = slideNumber;
		// setCaption(slideNumber);
	}
}

function setArrows() {
	if (document.images) {
		if (current == 1) document["lft"].src = rgt_off.src
		else document["lft"].src = rgt_on.src

		if (current + 2 >= thumbCount) document["rgt"].src = lft_off.src
		else document["rgt"].src = lft_on.src
	}
}