How to detect Facebook Like button pressed and trigger event?

Question

Here is the example:

• http://www.facebook.com/UEvents?v=app_4949752878&ref=ts

These guys get people to click on Like button (in Step 1) first bef

Answer 1

When a Facebook tab is loaded, the fb_sig_is_fan parameter is passed in specifying if the current user viewing the tab is a fan. Clicking on the Like button will trigger a reload of the tab content, resulting in an updated fb_sig_is_fan being passed in so the app can decide to show a different image.