[XBL] Pseudo-element

Dear XBL experts,

This email comments on the 7 September 2006 LCWD of XBL 2.0.

In Section 2.8, could you define what is a "pseudo-element" ? Could you 
a link to the CSS specification probably.

Why the example uses both xbl:pseudo="value" and xbl:inherits="value" ? 
Is this some copy/paste mistake ?

Cyril Concolato