This page is a simple example of getting MIDI input and output from and to a controller using the Web MIDI API. This example is designed around the Livid Controllers Base, Alias8, and CNTRL:R. At the time of this writing, Chrome Canary and Chrome Stable (33) have the only such implementation. There are some basic examples of lighting LEDs, getting MIDI data printed into text inputs in the DOM, and a basic sequencer that colors squares in the webpage in sync with the LEDs on the Livid Controller.
You may want to visit the wiki that has technical data for Livid Controllers. There is also a chart of sysex messages in a Google spreadsheet
The Web MIDI flag MUST be enabled via chrome://flags/#enable-web-midi and make sure your Chrome is up to date via chrome://chrome/
Adapted from Chris Wilson's examples: Drum Machine MIDI Synth Metronome