There's Still No Such Thing as a Web Site:
Finding the �Site� Isn�t Simple
There�s just no way, as far as I can tell, to look at a URI and figure out what site it�s from. Some sites just aren�t hierarchical, sometimes the site isn�t rooted at the top level. For example, the root of ongoing is at http://www.tbray.org/ongoing/, but there are things that are part of ongoing that don�t start with http://www.tbray.org/ongoing/ and there are things elsewhere on http://www.tbray.org/ that are part of other web sites.[...]
Grabbing Pieces of Namespace Isn't OK
Now, let's assume that we could somehow find the 'root' of a web site by some magic. I just don't think it's OK now in 2003, when we're maybe 1% of the way into the Web's lifespan, to start gobbling up little bits of the namespace. As it is, the names robots.txt and favicon.ico are stolen forever, nobody will ever be able to use them for their own purposes again.
OK, so how about we go back to Plan A and define DNS SRV records for domains to point to these?
It is a way to avoid well known ports, and it could be a way to avoid well know relative URL's too.