Lightbox 2 allows you to add captions for your images by defining the title attribute of an HTML link element.

<a rel="lightbox" title="Your Caption Here" href="original.png">
  <img src="thumbnail.png" alt="" />
</a>

The Problem

The problem with the title attribute is that most browsers display it in a tooltip when you mouseover the image. This isn’t desirable behaviour especially if you have used HTML markup in your caption.

The Solution

To avoid the caption text showing up, you can make these modifications in your lightbox.js file:

Line #218:

Find:          imageLink.title
Replace with:  imageLink.getAttribute('rev')

Line #223:

Find:          anchor.title
Replace with:  anchor.rev

Now you can use the rev attribute instead of the title attribute:

<a rel="lightbox" rev="Your Caption Here" href="original.png">
  <img src="thumbnail.png" alt="" />
</a>

This is kinda ugly hack and does not validate against W3C recommendations, but at least it hides the tooltip.