Originally Posted by trevvytrev21:
“That imitates an excited spelling error of OMG, at least I think. A bit like how 'pwn' is used instead of 'own' in the gaming community.”
Mostly right, ZOMG is simply Oh My God with an additional Z showing you were so excited about typing you got it wrong. On internet gaming forums it's usually typed ZMOG though

However, pwn doesn't equal own in the same way, it's usually used in a negative sense and implies the originator of the statement got one over on the pwn-ee rather than simply being a mistype ie you got pwned in that last PvP (person versus person for those who don't play multi player games) encounter or "I pwned you".
A more equivalent mistype from the gaming world would be teh where the is incorrectly typed because you're doing something too quickly
ETA: Edited to add/Edit to Add.
^^ or /\/\ means this above and is usually quoted when the person you're agreeing with has posted directly before you.
There was a very useful sticky thread on the old BBC forums where we collated all the abbreviations usually used on the internet in discussion groups. Sadly there doesn't seem to be an equivalent over here.
Originally Posted by oulandy:
“That's what I thought too before I discovered the alternative that it was used for. It would be better to write Edit: instead of some mystifying abbreviation.”
No because Edit simply means you've edited your original post. ETA means you've ADDED something to the post, the two things are different.