I'd posted on a board and it posted the same message twice??? I thought double posting was against the rules, and it wasn't intentional u o u I just don't wanna get in trouble if thats the case!

Don't worry, you won't get into trouble for that. It's a glitch that happens from time to time. If the duplicate is exactly the same, it's obvious that you didn't mean to post twice.

What double posting refers to is deliberately making a second reply to a thread immediately after your last one, without waiting for someone else to reply first.

If it'll make you feel better, you can always edit any duplicates. Some people remove the repeated message and replace it with an explanation/apology for the glitch.

Edit: I see you've got a duplicate of this thread as well. When that happens, you can always ping the minimod of a board and ask them to lock the copy.

You're not going to get a warning for obvious accidental double posts like ever. There's ways to check and ways to fix it if it happens, most commonly pinging that forum section's minimods to lock the duplicate.