Changing Captions With Pictures Not Working

For this page here: [URL]. I have the following code for the photo gallery:
var thumbProportion = .17 // thumbnails are 32% of their full size;
var IE = false;
if (navigator.appName == "Microsoft Internet Explorer"){IE = true;}
function swapImg(nImg,nSwapImgClass,nFullSizeImg,nCaption){

var thumbImg = nImg;
var thumbImgAlt = thumbImg.alt;
var origFullWidth = nFullSizeImg.width;
var origFullHeight = nFullSizeImg.height; .....
IE ? attachEvent('onload', init) : addEventListener('load', init, false);
The pictures change fine, but I can't get the captions to change with them.