This whole topic makes no sense to me. How is running and operating a web site any different from what is provided by Server Fault? It sounds like Webmasters is intented to be about network administration relating specifically to websites. That seems awfully specific and would probably rule out 50% of what webmasters do.
Webmasters run and operate sites, but they are almost always web site designers as well. If they don't design sites, then they're just a network administrator (not that NA's are "just" anything, but Webmasters are a specialized superset).
To say that HTML and CSS are not part of a webmasters duty is unreasonable in my mind. In many ways, I think it's more important for webmasters to have a site like this because they're more likely to need help with HTML and CSS issues because their job descriptions are often more jack of all trades and will need more help with specific skills.
Webmastes makes sense to me as a specialization because being a webmaster does require a lot of different skills. But to say that some of thsoe skills aren't appropriate for this site makes it questionable as to why the site then exists.