I just stumbled upon a funny Steemit error message...

Steps to reproduce:

1. Go to Steemit.com
2. Open any post in a new tab.
3. Upvote the post within the post page.
4. Go back to the original tab and upvote the same post there as well.

It's basically preventing me from "double-spending" my vote and I love the way it is phrased.