Question

I just found out about the Skeleton boilerplate, which uses grids. This is the css on github: https://github.com/dhgamache/Skeleton/blob/master/stylesheets/skeleton.css

The different column classes are layed out .one.columns, .two.columns, etc.

I’ve not seen this syntax in CSS before.

Am I right to assume that .one.columns {} is different from .one, .columns {} in that the former affects only elements with class="one columns" while the latter affects both elements with class="one" and class="columns"?

That is:

.one.columns = .one AND .columns
.one, .columns =  .one OR .columns

Answer 1

.class1.class2 {} refers to all elements with both classes class1 and class2.

.class1 .class2 {} refers to all elements with class class2 which are descendants of an element with class class1.

.class1, .class2 {} refers to all elements with both/either class class1 and/or class class2.