Common typo among people who like to insert many exclamation points to the end of a sentence, caused by accidentally releasing the Shift key before the 1 key, and sending the message without previewing it to realize the typo had been made.

Often used on purpose to make fun of such accidents and the people who make them, or as part of leetspeak.

A similar but less-joked-about occurrence is the tendency to insert backslashes after a string of question marks.

Punctuation commonly used in l33tspeak that emerged from a typo.