You can acheive this using the
The function offers many more arguments, but the one I think you need is
include (string) Only include certain Pages in the
list generated by wp_list_pages. Like exclude, this parameter takes a
comma-separated list of Page IDs. There is no default value. See the
Include Pages in List example below.
So assuming your ID's for the pages HTML and CSS are 6 and 8 (change as
necessary), you'd use -
$args = array(
'include' => '6,8'