Long time ago [1] it was decided that category net-www should be retired, since the www-* categories exist for these packages.
However, if I look at the category, then most packages in it were created in 2006 or later. In my understanding, at least no new packages should be created in net-www. Another question is if the existing ones should still be moved to some www-* category? Ulrich [1] <http://www.gentoo.org/news/en/gwn/20040726-newsletter.xml>
