Web development is a broad term for the work involved in developing a web site for the Internet (World Wide Web) or an intranet. This can include web design, web development, client liaison, client-side/server-side scripting, web server and network security configuration. However, among web professionals, "web development" usually refers to the main non-design aspects of building web sites. Web development can range from developing the simplest static single page of plain text to the most complex web-based internet applications.
Some more advanced web developers will also have these interdisciplinary skills / roles:
GUI (Graphic User Interface) design
Flash Capabilities (animation, audio, video, scripting)
Web content management system Deployment and/or Content management infrastructure design, development and integration
Web applications development, integration and deployment
Web server stress testing (how much traffic can a web server running a specific application endure before collapsing)
Web site code optimization (which is an important aspect of search engine optimization)