Did you know you always post the hardware mac address of your internet adapter of your computer every time to surf to a web site.
no you don't.
only your ISP's Router sees your MAC address. all requests going "further" into the internet only use the ip address to identify you.
But even if the web server could see your MAC address, this would be no evidence at all since you can pretty much choose your MAC address by yourself. LEO always uses IP addresses to identify you because these are assigned by your ISP and cannot be spoofed by the user.
but anyway, if you're that paranoid why would you post proof of your illegal activities on the internet in the first place?
is there some website you can go to and it will tell you all the info it knows about you just by visiting the page?