after a quick search of the web, a good bet is that it will work with .mp4 with the h.264 codec.
what you can try is to render from ae (composition>add to render queue), leave the settings at 'best'. if you have audio in the comp, click the 'lossless' output module and enable audio. then set you file path and render.
this will produce a lossless .mov which you can take to a compression utility to compress to a .mp4 with h.264 compression. you might try
mpeg streamclip, it's free and multi-platform, just import the .mov and choose file>export to mp4. for the setting, choose multi-pass and b-frames, set audio as needed and then compress.
Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW