One of the most annoying thing within creating html pages is to find out if all your links work. Concepts superior to html and http usually maintain a database, which automatically is updated if a document is moved or deleted.
For local URIs (those which only refer to files), hsc checks
existence of documents in your html project.
When you refer to a non-existing local URI within your source, hsc
will display a warning message. This does not only include documents
which are refered to using the <A> tag, but also other data
like images being embeded with <IMG>.
For external URIs, no checks are performed.