http://steem.supply/ Website ( @dragosroua )
is mining without your consent so don't leave it open if you disagree with that practice.
You can download miner blockers like these on Chrome if you need:
Should that practice be tolerated?
Edit 1: Here's an exemple of what I would consider ethically correct mining in a website
Edit 2: I finally saw the warning after many many attempt to reproduce. I had to clear the cache and saw at the bottom of the page a 20 pixel high banner with jsecoin logo and a very small disclaimer about mining. A refresh of the page wouldn't not show it back. I propose that the website owner puts a small disclaimer at the top of his page that is more visible. That's all.