How to make a transparent border using CSS?

Question

I\'m trying to do something like this for a client who has a blog.

Answer 1

use rgba (rgb with alpha transparency):

border: 10px solid rgba(0,0,0,0.5); // 0.5 means 50% of opacity

The alpha transparency variate between 0 (0% opacity = 100% transparent) and 1 (100 opacity = 0% transparent)