Just like :active has an equivalent .active class, so should :hover and :focus.

I am trying to use ZeroClipboard on top of a bootstrap button.  ZeroClipboard overlays a flash movie on top of the button to enable copy-to-clipboard functionality.

The problem is that there is currently no clean way to cause the hover/active states to be reflected on the bootstrap button below the flash movie.

There is no way for ZeroClipboard to programmatically set the actual :active/:hover pseudo classes on the DOM button when the user mouses over or clicks on the flash movie, so it allows you to set a custom class that it will set on the DOM button instead.  Since there is no class for the hover state, unlike the active state, I cannot use this functionality.

I could theoretically use less to make this easy as well, by defining my own classes outside of bootstrap, like so:
  
  .btn.hover {
    .btn:hover;
  }

But unfortunately, less does not allow you to mixin pseudo-classes and this generates a syntax error.

The solution is to add a .hover and .focus class to bootstrap's .btn, just like :active already has an equivalent .active class.