This category is for homepages of people who have designed or participated in designing roleplaying systems or content for these (also called Authors), and not about software helping to design/create roleplaying related content (these would go into the Software category instead).
Many professional authors of role-playing games have their own web pages. Typically these have a lot of semi-official supplemental information that just didn't get published, errata, and links.
The difference between a website that should be here, that of a professional Roleplaying Author, and just an amateur hobbyist who has written her own campaign scenarios for her group is somewhat subjective, but is like the difference between an Author and a Writer. One has a noticeable quantity of work professionally published, the other hasn't.