Facebook invented the Open Graph protocol to control how content appears when shared. In the source of the login page or a profile, you will see tags like og:title , og:image , and og:url .
The first thing you will notice at the top of the source code is the standard HTML5 declaration ( <!DOCTYPE html> ), followed by the <html> tag, which usually contains language attributes (e.g., lang="en" ). view source https m facebook com
