
I would say it could be marking, as my 13 week old bitch would pee on everything that another dog had layed on. Stay consistant, with the toilet training, and give praise and treats when he does it when he is outside (or where ever you want him to toilet).
Plus, he still is young, so accidents are going to happen. Just I know with my bitch is was pure dominance. She doesnt do it now though, thank goodness!