Last month, Nintendo allowed Wii U users to access the Miiverse from any PC browser. Today, they’ve updated the browser client, allowing users to post messages on the Miiverse network. When the browser client first launched, users were only able to read messages remotely.
Players will also gain the ability to follow and unfollow other Miiverse users, delete messages, and change your Miiverse settings. The wait time between posts has also been changed (reduced to three minutes instead of five). Users are also able to view messages without a login if they are linked to those messages directly. Posts from an internet browser are currently limited to text only.
Unfortunately, Nintendo has no updates to give us on when a 3DS version of Miiverse will be available. Nintendo has assured us that 3DS compatibility will be added at a later date, but for now, 3DS users will have to make do with their PCs.
Source: Miiverse