Web development is the work involved in developing a Web site for the Internet (World Wide Web) or an intranet (a private network). ... Among Web professionals, "web development" usually refers to the main non-design aspects of building Web sites: writing markup and coding.While the terms "web developer" and "web designer" are often used synonymously, they do not mean the same thing. Technically, a web designer only designs website interfaces using HTML and CSS. A web developer may be involved in designing a website, but may also write web scripts in languages such as PHP and ASP.