What do two dots in a CSS declaration mean?

Question

This is a bit of code from Twitter Bootstrap

.navbar .nav.pull-right .dropdown-menu,
.navbar .nav .dropdown-menu.pull-right {
  left: auto;
  right: 0;
}
         


        

Answer 1

The selector looks for any element with the class nav that also has a class of pull-right:

As a side note, the order doesn't matter both in the selector and in the class attribute.