The network protocol determines the underlying Internet protocol to be used to reach the location; it consists of a standardized name of a protocol followed by a colon and two forward slashes (://). Common protocols in URLs include ftp://, http://, and mailto://.

The host immediately comes after the protocol definition, represented by its fully qualified hostname, as found in the DNS or by its IP address. For example, a URL of http://www.askme.com contains both the protocol and the host data required to access this Website.

The file part of a URL defines the location of a resource on the server. Resources are files that can be documents, graphics, or plain-text files.

A URL such as http://www.askme.com has an implicit file location that most Web servers (for example, Apache) interpret to refer to a specific filename such as “index.htm.” All other files exist in a hierarchical directory structure under the root, such as /library/glossary/abglossary .htm. A full URL would look like this: http://www.askme.com/library/glossary/abglossary.htm.

When creating HTML pages, developers can choose to use relative file locations—such as “../pics/image.gif,” which locates the file “image.gif” in a subdirectory “pics’ of the directory containing the current file—or complete URLs, but most on the Internet use complete URLs.

See Also: Browser; Domain Name System (DNS); HTML or HyperText Markup Language; HTTP (HyperText Transfer Protocol); Internet; IP Address.