I have a screen capture video which I compressed to MPEG4 using Sonenson Squeeze 4.1. It looks great -- sharper than Sorenson 3, but when I upload it to my website I get an error when users click on it -- something like QT doesn't support this MPEG4 codec. You click through the error (which occurs only on PC's trying to play it not Mac) and then it plays!
So we have switched over to Sorenson 3 which plays cross platform with no errors, but the MPEG4 just looked better. What was going on? No MPEG4 on PC versions of QT?
Well, Sorenson Squeeze's MPEG4 output shouldn't look better than its SV3 output, but that is another matter (for MPEG-4, only Compression Master 3's encoder output approaches SV3 IMO). It sounds like you encoded to MPEG-4 using Advanced profile, but since you can ultimately play the video anyway, maybe that's not the case. Have you tried hosting the file on the web in a .mov container rather than a .mp4, if that's what you're doing?
Can I change the host by just changing the extension?
No. You need to open the movie in QT Pro, choose to delete the two MPEG-4 profile tracks (the non video/audio tracks) from the Edit menu, and then choose to do a Save As. Once you save this new file, you will have a proper QT .mov movie.