This is one of the weirdest bugs I've ever seen, I think.
One of the tags on this question is "javascript" but on the SO homepage, it shows up as "javas." If you click on it, that even takes you to https://stackoverflow.com/questions/tagged/javas (which has zero questions).
In the time it took me to write this up, the error seems to have been fixed (and that question closed) but I took a screenshot before that happened. It's the fourth question from the top.