I have yet to learn PHP first of all. As far as I know, JSP can do everything that PHP and ASPX can do. A programmer who knows JAVA and JSP can do almost anything. They work together very well. If one knows JS too, then every base is fully covered. JS isn't the most important, but it can do operations in realtime, onload or whenever, with out requiring the server. JS, JSP and JAVA can all communicate to each other, for the most part. Inline JS can't do as much, but it still does plenty. JAVA and JSP can access mySQL and other db's. I can't think of anything they can't do.