If you have email signup forms on Facebook, you might want to take a look at this: the Facebook developers site tells that FBML, the Facebook Markup Language, will be deprecated as of June 1st this year.

This gives you just over a month to update your signup forms on your Facebook pages: if you used FBML, it will be broken after June 1st. Use HTML/CSS and Javascript for the signup forms on Facebook to make sure they will work after that date. Read more