[XBL] Editorial: no link to pseudo elements

[Marcos Caceres]

In section 2.8, maybe you could include a "see Matching 
Pseudo-Elements"  after the text "The valid pseudo-elements are "value", 
"choices", "label", "repeat-item", and "icon".

So it would read:
The valid pseudo-elements are "value", "choices", "label", 
"repeat-item", and "icon" (see Matching Pseudo-Elements).

The first time I read this, I was unsure as to where these 
pseudo-elements were being defined in the spec (or if they where defined 
in some other CSS spec? or both).