I'm using Mozilla Firefox in Linux and I get
'mplayerplug-in
Playing video/wingsofapollo.wmv'
followed by film of a rocket launch.
But that's not really what you're asking, it's about Firefox on your own computer. I assume that your version of Firefox has the mplayer plugin. It's the sort of mistake I make
Otherwise you'll have to ask someone with better technical knowledge than me!