Web developers on ASP.NET have (mostly) a client or client-server background.
Web developers on Java have (mostly) a client-server background or a web background.
PHP and Ruby and Pyton (and so on) ones have only web development background or even web design background.
This is just a quick idea that came to my mind this evening while running, and I wanted to share... I think I'll elaborate more on this in a following post.
PS: I know, there are exceptions to these statements (as I am, since I was born as web developer and I develop on ASP.NET), but for the majority of developers this is true.