Diagram of quality control logging tool (2007)
This diagram explains the messages from a quality control tool I wrote in Opera to assist web developers in testing their content pages.
This was before I discovered libraries like YUI test and QUnit and firebug—but the idea is much the same. The tool was a script and stylesheet setup in the "author view" for Opera.
As you browsed web pages, it reported issues like last modified metadata not matching the displayed last updated date, metadata claiming the page was 'invalid' or HTML that didn't match the patterns we had documented for various content types.