EF_Simone:
Don't you mean "worst error"?
Fail is slang. When you do something stupid, you fail. When you hurt yourself, you fail. In teenage vernacular, it is a way to rudely point out others' less-than perfect moments. Yelling "You fail!" or "Epic fail!" is a cruel way of bringing attention to someone's misfortune. When I think about it, "fail," as used by teens, is more of an interjection (kind of like WTF, OMG, epic, or woot).
So ... the grammar isn't the best in the original post making the meaning unclear, but I believe that the author is using "fail" in the slang. I still can't figure out what the author is after though. Why this as a first post?
Eric Noto