1111? 11 eleven?? Eleven eleven???

Factual Questions
1

I have seen this “eleven eleven” thing crop up a lot in instant messaging and the like.

What does it mean exactly and is there a “proper” way to write it (from the choices in the title or some other way)?

2

This was just done.

3

Bah…figures.

I did a search for this but either the hamsters are tired or (more likely in this case) the “version” of eleven eleven I used to search was off.

Thanks.