Facebook scrapes information from web pages periodically and stores that information for easy retrieval in the future. If you are needing some changes to populate immediately, you need to prompt Facebook to rescrape the web page again for new content.This can be accomplished with the Facebook Object Debugger.
  1. Visit the Object Debugger.
  2. Input the URL and select Show Existing Scrape Information to view what Facebook has stored about the URL.
  3. If you want to update this information, select Fetch New Scrape Information.
For more information on how to hard code some of the information that appears on Facebook, visit How can I choose the image thumbnail that shows up on Facebook?