Make an element in a multiple list unselectable???

Is it possible through css to make an element in a multiple list
unselectable. Im organizing my list by using titles...

+-------------+

CATEGORY 1 |
option 1 |
option 2 |
option 3 |
CATEGORY 2 |
option 1 |
option 2 |
option 3 |
CATEGORY 3 |
option 1 |
option 2 |
option 3 |
+-------------+

Id like to make the CATEGORIES unselectable. Thanks! -Nick