Packages for file-finding & disk-usage

[Robert Thorpe]

I'm looking for two packages.  I don't know if anything exists for these
use cases:

* HTML dependency finding.

I often write webpages.  I work by saving files in a tree of directories
used by a web-server.  Given "<a href=".../foo.html">Foo</a>" in a
HTML file, I'd like to be able to easily tell if foo.html exists.  For
example to put point on it and see a message in the echo area like "file
exists" or "file not found".  Is there a package to do that?

* Disk usage.

I'm looking for a tool to monitor disk-usage.  I want to know things
like how much space the files in a particular directory take up.  Also,
what type of files use what amount of space.  Is there a way of doing
that within Emacs?

BR,
Robert Thorpe