Whenever Facebook visited a page (most probably when someone shared your URL on Facebook), your page’s metadata will be cached. I am not sure when the cache expires, but you can actually clear the cache easily by directing your browser to this address below
Few months ago, Facebook removed the page that allow us to generate codes for their official “Share” button. They replaced it with “Like” button instead. While “Like” button is fast and easy but we cannot add our comment along with the “Like” action. Therefore, in some cases, we still need the old Share button. Fortunately, the sharer.php still exists, so we can add the Share button using Facebook’s official script.
If you are regular Facebook user, which I am sure most of us here are, you will notice a new feature which I believe its known as “theater”. When you click on a photo, you will not be brought to photo page anymore, instead, you will stay on the page and a theater-style photo viewer will popup for you to browse and comment on the photo.