I had no idea that was even being rendered. Yes, something strange is going on. I had an issue a while back where I was adding a container somewhere, but I forgot to close a style tag and the entire site tried to load as a style, it gave me a server error and I didn't realize until the next day that the entire index page was a style, lol. After that day some odd things are going on in the site, pages duplicate themselves about 10 or so times and I have to backup, delete the site, and re-upload for it too work. It's an issue in confliction with wordpress, and I'm not surprised fancybox loads, al it is is a javascrpt that tells an image to popup in a frame with a ice jaascript effect. Pretty simple actually, lightboxes are.
I'm currently working out the strange pre-head you've noticed. It must be recent, because I would notice that... hmmm
Anyway, try and focus on the lightbox positioning. Is there any way to simple have fancybox load the image 400px higher? Seems like a simple solution, might mess it up on other pages though, so I'll do some other tests.