Is it possible to post something in a website and not be able to be tracked down?

Say you post something on a website from a computer or an iphone. Can the cops track your location and find you? If yes then how can i post something without being tracked? If i do it from an iphone is it still possible to be tracked?

Let me put it this way. You're connected to an ISP of some sort. EVERYTHING you say and do is / can be pulled up.

When you're watching nudie films and shopping for fun things, the ISP will see it.

PC name and phone name just tell them who it is

Technically you can't. There are software out there that will manipulate sites thinking you have a different IP address and such. All of this can be tracked if someone really needs to figure out who posted something or where the post came from. Just don't post it.