html 5 video on iphone

I did this once and I can't do it again.

I have a bunch of mp4 movies. I need to know what encoding settings to use to get them to play in mobile safari using the <video> tags.

I've tried h.264 640x480 different bit rates, different video sizes, i tried mpeg-4 of different sizes and bit rates. I just don't know of anything that works. I even read the specs off apples site. I have video converters, plus I tried using quicktime pro and quicktime X to use their own "export to iphone" and that still doesn't work.

on the iphone i just get the video with a play button Xed out.

Any help would be great!

Thanks!