It says the following
How did this happen, this site really is cryptic
How to do it
It's a substitution cipher which can be decoded using the following substitutions (replace top letter for bottom)
ABCDEFGHIJKLMNOPQRSTUVWXYZ FEDCBAZYXWVUTSRQPONMLKJIHG
In other words to decode
Use a reverse substitution cipher shifted by six places. This cipher is symmetric, so encoding is done in the same way.