Most universal video format? Options

[baytonemus]

I'm adding video to a site for the first time. I was thinking that QT would probably be the most universal cross-platform format. Of course, the first person I asked to test it for me, (my mother-in-law - the last person I know who still has a dial-up connection), got an error message saying she didn't have it installed.

I'm a Mac user. Doesn't IE automatically install the QT plug? She may also have an older version of IE as well as Windows.

Second question, is IE pretty intolerant of spaces in file names? I had posted a .mov file for testing which I had carelessly not renamed to remove spaces and it wouldn't load in IE6. It's obviously an easy fix but I'm just curious.

Thanks - JAY