The Internet connects two kinds of computers: servers, which serve up documents, and clients, which retrieve and display documents for us humans. Things that happen on the server machine are said to be on the server side, and activities on the client machine occur on the client side.
To access and display HTML documents, we run programs called browsers on our client computers. These browser clients talk to special web servers over the Internet to access, retrieve, and display electronic documents.
A variety of browsers are available today. Internet Explorer comes with Microsoft’s operating system software, for example, while most other browsers are free for download on the Web. And most browsers run on client devices that have high-resolution, high-color graphical viewing screens. In fact, today’s browsers share common HTML-rendering software under the hood, so to speak, and differ only by extraneous, albeit some very useful features. For instance, when you install Netscape Navigator version 8, you decide whether to use the NCSA Mosaic rendering software, portions of which also are under Microsoft’s Internet Explorer, or Mozilla’s software, which comes under the hood of another popular browser, Firefox.
This is very different from around the turn of the century, when Internet Explorer savagely competed with Netscape Navigator through unique extensions to the HTML language. Internet Explorer won. Many of its extensions even became HTML standards, and others such as Netscape’s layout extensions disappeared and so got relegated to appendices in this book.