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HTML - URLs Explained

URLs, or addresses, provide a standard way of locating resources on the web. Resources may include HTML files, graphic files, Flash files etc.

URLs that refer to HTTP, the protocol that web pages use, are made up of a number of elements - some of which may be omitted.

An Example of a URL

http://www.webdesignworkmate.co.uk:80/scripts/page_1.php?name=Fred#here

If the example above is broken down.

The Scheme: http - This refers to the protocol and where a connection is made to request a web resource. This will normally be http. If the connection is to a secure server it will be https and if the request is for a file resource, it will be ftp.
The Host: www.webdesignworkmate.co.uk - This identifies the machine running as a web server. It's normally identified as a domain name which acts as an alias for the IP address of the machine.
The Port: 80 - This is optional and if omitted assumes port 80 for http requests.
The Path: scripts/page_1.php - This represents the location of the requested resource relative to the document root of the server. In the example URL above, the requested resource is called page_1.php and is located in the directory, or folder, called scripts located in the document root.
The Query String: name=Fred - This is used to pass additional information to the requested resource. In the example URL above, the variable called name is set to the value "Fred" and passed to page_1.php. This is an example of a name-value pair where the name and value are separated by the equals sign. Additional name-value pairs can be sent by separating each with the ampersand character, as in this example. Name=Fred&age=26.
The Fragment: #here - This is used to refer to a specific section of a resource. In the case of HTML documents the fragment identifier refers to an anchor tag within the document so in the example URL above, the fragment refers to an anchor tag within page_1.php thus
<a name="here">An anchor</a>
The fragment is used by the web browser, not by the web server, to cause the page section from the anchor downwards to be displayed at the top of the web browser window.

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