Current source code:
HTML 5.0 [*] Partly supported, Partly: satisfying 60-90% of the specifications.
For Video & Audio. Note that webm is not supported in emulator.
Reference http://developer.lge.com/webOSTV/develop/web-app/webos-tv-platform/web-engine/ http://developer.lge.com/webOSTV/develop/web-app/webos-tv-platform/supported-media-formats/
I found the answer; I used a converter to support fallbacks in the browser. See this: http://easyhtml5video.com/