The "JavaDoc Output Generated by the Standard Doclet" specification[1] added in JDK-8261930 contains sections documenting the CSS classes used in API documentation generated by JavaDoc. These sections are generated automatically from jdk.javadoc.internal.doclets.formats.html.markup.HtmlStyles enum. However, not all CSS classes are of interest to users of javadoc. What's more, these CSS classes may change on a somewhat regular basis, which theoretically amounts to a specification change that requires a CSR.

In order to avoid these issues, we should implement a mechanism to exclude internal CSS classes from the output speicification, allowing us to have a better defined and more stable set of specified CSS classes.