The lightbox is trying to load up a blank image. The problem comes because of how you have initialized your lightbox. Your selector is set as $('#gallery a')
which is fine in some cases, but inside of your <div id='gallery'>
you have a link that doesn't contain an image.
To correct this I suggest the following changes:
initialize your lightbox like this -
$('a.gallery').lightBox(); //This selects all links with class="gallery" and adds them to lightbox
Then for each link on the page you what included in your lightbox add the class gallery
for example
<a href="siberianCats/SiberianCat-9.jpg" class="gallery" style="border:1px solid #8A8DA7" title="Siberian Kitten">
<img src="siberianCats/SiberianCat-9.jpg" alt="Fuzzy Siberian Cat and Siberian Kitten" title="Fuzzy Siberian Cat and Siberian Kitten"/>
</a>
For extra credit, you could then move the style declaration into your styles.css css file like so:
a.gallery{
border:1px solid #8A8DA7;
}
On a side note, you should only use an id 1x per page. Classes are used for non-unique DOM elements.