Nintendo made Miiverse accessible via PC and mobile browsers yesterday, giving you the chance to interact with the (not so wide) Wii U online community while away from your console. But as Nintendo notes at the bottom of the Miiverse page, "[S]ome devices may not be able to access it."
What devices, you ask? Why, the Wii U and 3DS browsers, of course!
Why you would want to visit the Miiverse website on the Wii U when the native app is sitting right there, I have no idea. Still, attempting to do so will display the above message, politely asking you not to return to the home menu and open Miiverse from there.
The 3DS message is a little more harsh, reading, "Browser error: The Internet browser you are using cannot be used to access Miiverse." Nintendo is planning on releasing a proper Miiverse 3DS app in the near future, but in the meantime, there will be no sneaking around Nintendo's carefully constructed walls! Shame on you hooligans!
Oh, and if you were curious, DSi and Wii browsers are likewise locked out.