I am interested in learning more about ssi... can anyone point me to some useful sites?

Exactly what can I do with it? Can I use it to make it easier to update, say, my menu? Like if I put all of the stuff on the left collumn of my page that is the same on every page into one file, could I do that? That way when I want to, say, add a section I would just have to edit one file, instead of 45?

Also, is ssi compatible with all browsers? am I gonna be screwing ns and opera users?

Thanks