When building mobile web apps (not physical apps) for the Samsung Galaxy S4 and S4 Active, the native Android web browser has broken support for the CSS rule border-radius. For more information, photos, and sample code, see the Stack Overflow posts:

http://stackoverflow.com/questions/17186158/galaxy-s4-stock-browser-css3-border-radius-support

http://stackoverflow.com/questions/17973394/border-radius-not-working-in-modern-native-android-browser

Basically, if you use border-radius anywhere in your CSS, the native Android web browser on this device ignores it. But if you use the long-form CSS property of border-right-radius, border-left-radius, etc, it recognizes it. In essence, part of the base CSS3 support is broken in this browser for rounded borders. Other Android web browsers (including the Galaxy SIII) in other devices properly handle this CSS rule.

This is a bug in the browser itself.