How does CSS specificity decide which styles to apply?

Question

How does CSS determine when to apply one style over another?

I have been through the W3 CSS3 selectors document a few times, and that has helped me understand how to

Answer 1

It's based on IDs, classes and tags. IDs have the highest specificity, then classes then tags, so:

.item a     == 0 1 1      0 (id) 1 (class=item) 1 (tag=a)
.special    == 0 1 0
#foo        == 1 0 0
#foo .bar a == 1 1 1
#foo #bar   == 2 0 0

whichever has the most wins :) If it's a tie, whichever one comes last in the document wins. Note that 1 0 0 beats 0 1000 1000

If you want .special to apply, make it more specific: .item a.special