Ill check the precise settings in VS10 ( just tinkering with it) . As stated wmv seems to offer the best quality/ space ratio.
And all PCs have media player which can play it. Saying that , Quicktime and Real media are other formats which are usable. At any rate there are standalone video conversion software which can turn an AVI, mpeg ect to any of the formats suitable for web streaming.
Some online sites allow you to upload your small video clips for free ( in the same way you can upload stills to an online album) and you could then put a link on your web page pointing to the hosted clip.
Another method is to point the link to a hosting site for downloading and playing on the indiviual Pc instead of streaming online
HTH