So what there is always room for improvement, but things change. So what should a new webmaster study to stay abreast of the latest and greatest?
That depends on what kind of work you are interested in. Working for medium-sized businesses or freelancing might be best served with PHP; big businesses—the fortune 100- or even 1000 companies—will require either .NET or Java. Or you may want to take your career somewhere else entirely. You will have to tell us more about what you actually want to do and what you already know before we can offer useful recommendations.
I would work on understanding search engine optimization. A lot of folks consider search engine optimization is an after-thought after web design. But in reality, they are closely related. I have seen so many sites that were built not search engine friendly. It is rather costly to rebuild those sites in order to increase their rankings.
As feellikeanut said, depends on where you're going, but in general I'd just build more websites to increase experience and maybe start looking at the new stuff in css3. Thats all I can think of.