Just something I found for Wordpress users,
As obvious as it sounds, If your div is returning some AJAX content based on say a header that would commonly link out to a new post page, some tutorials will say to return false since you're returning the post data on the same page and the return would prevent the page from moving. However if you return false, you also prevent Fancybox2 from doing it's thing as well. I spent hours trying to figure that stupid simple thing out.
So for these kind of links, just make sure that the href property is the hashed (#) div you wish to select, and in your javascript, make sure that you do not return false since you no longer will need to.
Simple I know ^_^