I have written a simple WebView app and tested it on android 2.3. When I press the up/down arrow keys the selected buttons is highlited by an orange frame. I've tested this application in the emulator with android 4 and there is no highliting. I can still navigate with the keyboard and press the buttons but there is no selection indication.
I found the answer: My project had an old api version: (8, for Android 2.2). Replacing it with 15 solved the problem.