css3 nth of type restricted to class [duplicate]
Unfortunately, there is no way (at least none I know of) to select nth-of-type of a class, since nth-of-class doesnt exist. You will probably have to add a new class to every third .module manually.
It seems what you really want is the css4 :nth-match selector, but it's not really supported in most browsers yet, so currently, the only way to do it is with javascript
$(".featured.module").filter(function(index, element){
return index % 3 == 2;
}).addClass("third");
http://jsfiddle.net/w3af16dj/