When you want to access a web page, or "other resource" on the Web, you normally begin either by typing the address of the web site in your browser (Internet Explorer or Mozilla/Firefox), or by following a hypertext link to that page or resource. Hypertext links are the fundament of the World Wide Web. Thus a webpage is a simple text file write in a description language called HTML (HyperText Markup Language) allowing the description of the page contents and the possibility to include graphics elements or links to others documents.
Beyond hypertext links, the web is based on HTTP protocol allowing to link documents that are on located on different computers (called web servers contrary to clients represented by web browsers).
What is an URL?
On the web, all documents are located by an unique address, called URL (Uniform Resource Locator), allowing to locate a resources on any server on the Internet.
An URL is represented like that:
An URL consists of three parts:
These are the shortest address forms and should be used for bookmarks and as references from other sites.
When you browse such an URL it will instruct the browser to jump to the correct place.
http://www.cern.ch/web makes the browser jump to http://webservices.web.cern.ch/WebServices/
The long address form is needed in order to implement a namespace and hide the underlying physical implementation. Both the short and the long address form are stable (never changes), but the hosting server behind address can change from one day to another.
You can distinguish between different site types by looking at the final, redirected address :
- Official web sites are on the form : http://SITENAME.web.cern.ch/SITENAME
- Personal web sites are on the form : http://SITENAME.home.cern.ch/SITENAME
- Test sites are on the form : http://SITENAME.webtest.cern.ch/SITENAME
What is a web site?
A web site is usually set of Web pages around a central page, the so called "Home page" and offering lot of links to a collection of others pages located on the same web server. In addition to links interconnecting the pages within a web site, there are also "external links", pointing to pages on other servers.