This new feature in v1.5.1 sounds like a great idea, but I'm not sure how practical it is. I composed a small test for a stock Zen Cart v1.5.1 install, creating three files in /includes/templates/classic/css:

c_54_children.css: .centerColumn { color: green; } ... New v1.2
c_54_55.css: .centerColumn { color: blue; } ... New v1.2 ... Discount Qty
p_127.css: .centerColumn { color: red; } ... New v1.2 ... Discount Qty ... Normal Product

My expectation and the actual text color for the various pages are as follows:
Code:
main_page=index&cPath=54, expected=black, actual=green
main_page=index&cPath=54_56, expected=green, actual=green
main_page=index&cPath=54_55, expected=blue, actual=green
main_page=product_info&cPath=54_55&products_id=127, expected=red, actual=green
My expectation for cPath=54 being black is that it's not a child of itself so the _children file shouldn't have been loaded. I expected that the c_54_55.css file would override the c_54_children.css in standard CSS fashion; ditto with the p_127.css as it was more specific.

Am I simply harboring false expectations or is this a problem with the way the _children.css files are loaded?