url link blocking. What happened to it.

So when someone submitted a url at least at one point it would show up on the right and you could block it. So if someone posted a newsweek link you could block any link postings from like newsweek.com or maybe reddit.com or google.com. Lately though I have not been able to. It seemed to disapear at some point. I have not seen it as an option in a long time.