The working form of the link is as:
		<a href="images\image-1.jpg" title="This will be the caption">image #1</a>

If I understand this correctly, it is defined in the js file here:
		var objCaption = document.createElement("span");
		objCaption.setAttribute('id','caption');
		objImageDetails.appendChild(objCaption);
Which becomes:
		<span id="caption"></span>

I'm trying to have the output something as:
		<span id="caption"><?imgString(caption,15);?></span>

I also see this near the end, this is what's creating the span output?
		// if caption is not null
		if(imageArray[activeImage][1]){
			Element.show('caption');
			Element.setInnerHTML( 'caption', imageArray[activeImage][1]);
		}