• The primary function of a web server is to deliver web pages (HTML documents) and associated content (e.g. images, style sheets, JavaScript’s) to clients. A client, commonly a web browser or web crawler, makes a request for a specific resource using HTTP and, if all goes well, the server responds with the content of that resource. The resource is typically a real file on the server’s secondary memory, but this is not necessarily the case and depends on how the web server is implemented.
  • While the primary function is to serve content, a full implementation of HTTP also includes a way of receiving content from clients. This feature is used for submitting web forms, including uploading of files.
  • Many generic web servers also support server-side scripting (e.g. Apache HTTP Server and PHP). This means that the behavior of the web server can be scripted in separate files, while the actual server software remains unchanged. Usually, this functionality is used to create HTML documents on-the-fly as opposed to return fixed documents. This is referred to as dynamic and static content respectively. 

History of web servers:

  • In 1989 Tim Berners-Lee proposed to his employer CERN (European Organization for Nuclear Research) a new project, which had the goal of easing the exchange of information between scientists by using a hypertext system. As a result of the implementation of this project, in 1990 Berners-Lee wrote two programs:
    • a browser called Worldwide Web;
    • The world’s first web server, later known as CERN httpd, which ran on NeXTSTEP.
  • Between 1991 and 1994 the simplicity and effectiveness of early technologies used to surf and exchange data through the World Wide Web helped to port them to many different operating systems and spread their use among lots of different social groups of people, first in scientific organizations, then in universities and finally in industry.
  • In 1994 Tim Berners-Lee decided to constitute the World Wide Web Consortium to regulate the further development of the many technologies involved (HTTP, HTML, etc.) through a standardization process.
  • Common features
    • Virtual hosting to serve many web sites using one IP address.
    • Large file support to be able to serve files whose size is greater than 2 GB on 32 bit OS.
    • Bandwidth throttling to limit the speed of responses in order to not saturate the network and to be able to serve more clients.