Please don't beg. You are a grown person (hopefully), and people are not going to answer for very long if you keep this plead of despair up. You're here to get help, indeed, but you need to earn help. Show that you're trying.

MediaWrap (the plugin for Firefox) is not available for the N900, and will most probably never be. Rather than explaining what Add-on you want, it may be more helpful to explain what you are trying to achieve?

Yes, you said you wanted to play media files, but maybe you could show an example, and some of us may use our N900 to see if we can play it, or come up with a solution for you?

Please, don't be begging for help. There's nothing more insulting.