Help Questions for User Made Scenarios

[MacD2013]

Having some problems in being able to download these from the Unity webpage. Was wondering if there's something I'm missing (quite probable). I go into the game tab that says user scenarios and there's nothing in the file. I can't really download them from the webpage as when they're downloaded the file says it can't be opened. I'm a Mac user so does that have something to do with it?

Thanks!