Web Development can be split into many areas and a typical and basic web development hierarchy might consist of;

Client Side Coding

CSS
XHTML (in accordance to modern web design standards, XHTML’s use is replacing the older HTML)
Javascript

Server Side Coding

PHP and MySQL
ASP and MSSQL
ASP.NET and MSSQL
CGI and/or Perl
Java, e.g. J2EE or WebObjects
Ruby, e.g. Ruby on Rails
ColdFusion

In [...]

Since the mid-1990s, web development has been one of the fastest growing industries in the world. In 1995 there were fewer than 10,000 web development companies in the United States alone and in 2005 there are over 30,000 such companies.[1] The web development industry is expected to grow over 20% by 2010. [...]

Web development is a broad term for any activities related to developing a web site for the World Wide Web or an intranet. This can include e-commerce business development, web design, web content development, client-side/server-side coding, and web server configuration. However, among web professionals, “web development” usually refers only to the [...]