HTMLProofer is a set of tests to validate your HTML output. These tests check if
your image references are legitimate, if they have alt tags, if your internal
links are working, and so on. It's intended to be an all-in-one checker for your
output.

In scope for this project is any well-known and widely-used test for HTML
document quality. A major use for this project is continuous integration -- so
we must have reliable results. We usually balance correctness over performance.
And, if necessary, we should be able to trace this program's detection of HTML
errors back to documented best practices or standards, such as W3
specifications.