or 'navigating the Web'. Early studies of this new behavior investigated user patterns in using web browsers. One study, for example, found five user patterns: exploratory surfing, window surfing, evolved surfing, bounded navigation and targeted navigation. The following example demonstrates the functioning of a web browser when accessing a page at the URL . The browser resolves the server name of the URL () into an Internet Protocol address using the globally distributed Domain Name System (DNS). This lookup returns an IP address such as 203.0.113.4 or 2001:db8:2e::7334. The browser then requests the resource by sending an HTTP request across the Internet to the computer at that address. It requests service from a specific TCP port number that is well known for the HTTP service so that the receiving host can distinguish an HTTP request from other network protocols it may be servicing. HTTP normally uses port number 80 and for HTTPS it normally uses port number 443. The content of the HTTP request can be as simple as two lines of text: GET /home.html HTTP/1.1 Host: example.org The computer receiving the HTTP request delivers it to web server software listening for requests on port 80. If the webserver can fulfill the request it sends an HTTP response back to the browser indicating success: HTTP/1.1 200 OK Content-Type: text/html; charset=UTF-8 followed by the content of the requested page. Hypertext Markup Language (HTML) for a basic web page might look like this: <html> <head> <title>Example.org – The World Wide Web</title> </head> <body> <p>The World Wide Web, abbreviated as WWW and commonly known ...</p> </body> </html> The web browser parses the HTML and interprets the markup (<title>, <p> for paragraph, and such) that surrounds the words to format the text on the screen. Many web pages use HTML to reference the URLs of other resources such as images, other embedded media, scripts that affect page behaviour, and Cascading Style Sheets that affect page layout. The browser makes additional HTTP requests to the web server for these other Internet media types. As it receives their content from the web server, the browser progressively renders the page onto the screen as specified by its HTML and these additional resources. HTML Hypertext Markup Language (HTML) is the standard markup language for creating web pages and web applications. With Cascading Style Sheets (CSS) and JavaScript, it forms a triad of cornerstone technologies for the World Wide