Web developers create and maintain websites. They are also responsible for the site`s technical aspects, such as its performance and capacity, which are measures of a website`s speed and how much traffic the site can handle. ... They are responsible for the look and functionality of the website or interface. A web developer is a programmer who specializes in, or is specifically engaged in, the development of World Wide Web applications using a client–server model. The applications typically use HTML, CSS and JavaScript in the client, PHP, ASP.NET (C#), Python, Node.js, Go or Java in the server, and http for communications between client and server. A web content management system is often used to develop and maintain web applications. ©