Son Order List <ol> anidados :)
Y usas ahí counter y conter-reset
12 Generated content, automatic numbering, and lists
http://www.w3.org/TR/CSS2/generate.html
Make an ordered list go up as 1.1,1.2,1.3 instead of 1,2,3.
http://doctype.com/make-ordered-list-go ... nstead-123
Is it possible to add subitems into an ordered list?
http://doctype.com/possible-add-subitems-ordered-list-6