border-radius not working in modern native Android browser
Turns out, this issue is specific to the Android browser on the Galaxy S4 and S4 Active. It looks like they've broke support for the condensed border-radius property, but if you specify each corner individually, it works fine. I'm posting a bug report to Android. So, if you do this:
border-top-left-radius: 10px;
border-top-right-radius: 10px;
border-bottom-left-radius: 10px;
border-bottom-right-radius: 10px;
It works fine; if you just have border-radius: 10px; it gets ignored.
This was answered under this post: Galaxy S4 stock browser CSS3 border-radius support? I'm just repeating it here. But I did test their solution, and it is working fine now on the Galaxy S4 Active as well.