Initiator jquery.min.js - 404 Not Found on ajax-loader.gif and black.png

I am starting to optimize a website that I have been working on for speed, using minified JS, CSS without comments, etc.

I was using chromes developer tools - network tab - to get an estimate of load times and to spot any errors. Here, I noticed two 404 not found errors for two image files: ajax-loader.gif and black.png.

After a quick google search I found an "ajax-loader.gif" generator with different versions of your standard pinwheel loader. I've generated one and included it in my files and it loads just fine now. But what initializes this gif? None of my jquery loads so slow as to require it. So how does this image actually get loaded, or rather when does it appear? Does jquery initiate it itself?

Further more I have black.png. I can't find any related material about this file, and it is quite clear that jaquery.min.js is initiating it. I am using google's api link to jquery library. What does black.png do?

Here is a screenshot...

You can see ajaxloader.gif there also, now working after I generated and uploaded one. Before I did so, it 404's like black.png obviously because it didn't exist, and took a similar 220ish ms latency, which is now less since it can find the file.

So to summarize, what do these do, when do they appear, and what is black.png actually?

The images appear to be getting loaded from gallery.js on line 69

$items.add('<img src="images/ajax-loader.gif"/><img src="images/black.png"/>')

http://khill.mhostiuckproductions.com/siteLSSBoilerPlate//include/head/js/img-gallery/gallery.js