Relative links are great; they let you move your whole tree of HTML
files from one place to another and still retain the internal link
structure. However, they start to suffer when you have multiple
levels of directory structure: is that href="../../style.css" or
href="../../../style.css"? It's a bit confusing, and even if you
don't get confused, you still have to modify links when you copy them
from one file to another.
What would be more helpful would be the ability to say "up to a directory named foo". Suppose you have this setup:
kragen/
index.html
resume.html
style/style.css
images/
kragenlogo.png
headshot.jpg
blog/
1.html
2.html
archive/
2008-03.html
Now, suppose there's some text in 2008-03.html that was originally
in 2.html or one of its siblings. It would be nice if that text
didn't have to be changed from <a href="1.html"> to <a
href="../1.html">. You can write <a href="/kragen/blog/1.html">,
but in addition to being verbose, that makes it hard to use a tree of
HTML that you've downloaded with wget -r or something similar.
Suppose you could instead write <a href="$blog/1.html">, meaning "go
up until you find an ancestor directory named blog, then use its
children". Now you can write things like <img
src="$kragen/headshot.jpg"> freely, and copy and paste them among all
the files.
By itself, this would be a backwards-incompatible change to browsers and the URL spec, but it could degrade gracefully. You could program your web server to generate redirects for backwards-compatibility, while implementing the change in newer browsers. Compatibility problems would only arise if someone had a relative link to a directory whose name began with "$" whose name otherwise duplicated that of a directory higher up in the hierarchy.