Why is the first Facebook request for the IFrame App Canvas Page a POST request?

Question

I noticed that today, when I installed my first FB application (the iframe application available on facebook), all requests made using facebook are POST HTTP messages, not GET. Is there a reason for this? What if I would like to implement HTTP caching?

I am new to development on the FB platform, forgive me if this is an obvious question, but I searched Google and cannot find the answer.

Answer 1

Facebook POST to the homepage to submit a signed request that contains potentially important information for the application.