Weird mp4 video problem

Hi all,

I converted one of my avi files with Handbrake and uploaded to my web server for testing purposes. The file itself works through safari or locally on quick time. However I couldn't get it worked through mobile safari on my iphone. There is a crossed play sign in the middle. Then I went further and synched the video to the phone and it works.

I was thinking the presets in Handbrake must be wrong for some reason but then it wouldn't work when I synched it.

Any ideas?