Commonly used in forums, chatrooms, and online games. Used to symbolise that whatever the previous or quoted person said had just completely failed, being a fail in grammar, or life. The / before the fail is derived from HTML language in which ending a function defined by a /. The / also emphasises how the person in question failed and should not continue to post moronic things on 'teh interwebs' as their father taught them, but to ask to have their passport and material possessions confiscated and have themselves shipped off to a third world country.