I'm really not sure if this is doable or not.
I'm working on a website at the moment third party companies can post content on this website.
For those companies we are going to include a Facebook like button so users can like them on Facebook.
When the page loads if there a way we can check and see if the user has already liked the brand? Assuming the user is signed in to Facebook.
Is they have we'd like to display slightly different content.
I think if this was my brand I could access the information via the API but with it being a third party I doubt that would work.