This demo contains two thumbnail sliders: one is horizontal and another is vertical.
If you use this demo's source code, and you only need one slider, you should remove the other slider from the source code.
For example, when you only need the horizontal slider, you should:
<div style="float:left;padding-top:98px;">
<div id="thumbnail-slider">...</div>
</div>
<div style="float:left;padding-left:100px;">
<div id="thumbs2">...</div>
</div>
<div style="clear:both;"></div>
<div id="thumbnail-slider">...</div>
<link href="1/thumbs2.css" rel="stylesheet" />
var thumbs2Op = { ... };
var mcThumbnailSlider = new ThumbnailSlider(thumbnailSliderOptions);//Note: this line is still needed.
var mcThumbs2 = new ThumbnailSlider(thumbs2Op);