Query number of users that like a page in facebook?

If I put a facebook like button on a webpag开发者_C百科e, can I use FQL to query the number of users that 'liked' the page?

Yep. Try the following FQL:

SELECT like_count FROM link_stat WHERE url="http://your-web-page-url";

There's more stats available from the link_stat table as well. The table reference is here.