Can someone explain why the last-child doesn't work when I use the class selector with it? Is this not allowed?
http://jsfiddle.net/T2PgX/2/
This is because :last-child your list is not .group1 .
:last-child
.group1
Selector li.group1:last-child doesn't mean "last li.group1 child"; it means "the element li that is the last and has the class" group1 ".
li.group1:last-child
li.group1
li