Flash is slowly dying.
Macs are no longer shipping with Flash installed but the user can download and install it.
Like Simon said encode your video as a MP4 and embed this in a Flash player.
Like I did on this page. On that page I provided a link to the mp4 file but there is also a way to have it automatically serve the mp4 video to non Flash devices as
explained on this page. I haven't done it this way yet but probably will next time I do an update.