The only new thought to add: some vids are made with poor source or were made pre-computer. Encoding quality and visability may vary (ex. I cannot capture the VHS versions of older vids to my computer so I can add titles/ do nifty encoding. I am able to cpature them to a stand alone DVD recorder and then rip that file and compress).

I like DivX and have been re-encoding some of my web vids full screen using the codec. Very nice.