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Exploring the World-Wide Web

URLs


This page describes:

URLs, or Uniform Resource Locators, are a standard way of specifying the location of Internet computer files. Using its URL, you can retrieve a file from any computer on the Internet (or tell someone else how to retrieve it).

URLs are very similar to e-mail addresses. However, they include additional information that makes them considerably more powerful.

Below, the URL for this page is analyzed part by part. Click on each part pf the URL for its meaning.

http://www.georgiacenter.uga.edu/Exploring/urls.html

http://www.georgiacenter.uga.edu/Exploring/urls.html

The first part of the URL identifies the protocol necessary to retrieve the file. The scheme "http://" indicates that the file is a web page (remember that HTTP stands for "Hypertext Transfer Protocol," the standard for web servers). You will also see URLs using other schemes, such as:

gopher://
Identifies a file on a gopher server.
news://
Identifies an item from a Usenet news group.
ftp://
Identifies a file that can be downloaded from an FTP server.

Web browsers can process URLs specifying other server protocols, so that a program like Navigator can also act like a gopher client, a news reader, and an ftp client.

http://www.georgiacenter.uga.edu/Exploring/urls.html

This part of the URL is in the same format as part of an e-mail address. It is the domain name of the machine on which the file is located. Understanding domain names can help you guess URLs. Interpreting this domain name from right to left, we can decipher some information about the computer:

edu
A U.S. educational institution. Other common endings for domain names are com (a commercial organization), org (a non-profit organization), and gov (a government organization).
uga
Identifies the University of Georgia subdomain. All computers at UGA that are on the Internet can register to use a name ending in "uga.edu."
georgiacenter
Identifies the University of Georgia's Center for Continuing Education.
www
A specific computer -- "www" is a common name for World-Wide Web servers.

http://www.georgiacenter.uga.edu/Exploring/urls.html

The last part of the URL specifies the fully-pathed filename for this page. "Fully pathed" means that the name tells what directory the file is stored in on the web server's hard disk drive (and if necessary what directory that directory is in, and so on). In this example, the file for this page is "urls.html" (the extension indicates that it is a text file in Hypertext Markup Language), and it is located in a directory called "Exploring."

Sometimes you will see a domain name followed by a single slash (for example, http://www.georgiacenter.uga.edu/). Entering this URL will retrieve the home page for that web server. Leaving off this slash sometimes produces an error.

URLs may seem long and cumbersome, but each part is necessary. When you consider that a URL tells exactly where the file is and how to get it, it's worth all that typing!

Using URLs in Netscape Navigator

 To see the URL for the current page in Navigator, make sure that "Show Location" is checked in the Options menu. This displays the URL in a box underneath the buttons.

You can type a URL into this box and hit the Return key to go to that page. In Windows or on the Macintosh, you can also use the cut, copy, and paste operations to enter a URL. For example, if you are using a Mac or Windows e-mail program, you can use the mouse to select and copy a URL from the body of a mail message, then switch to Navigator and paste it into the Location box.

Another way to do the same thing is by clicking on the Open button, which will present a dialog box in which you can type or paste a URL.

A feature which may not work in other browsers: you can leave off the "http://" part of the URL for a web page in the Location box or Open dialogue.

Guessing URLs

Often you can guess a URL that will get you into the neighborhood of useful information. Most corporations with World-Wide Web servers use a "canonical address" in this format:

www.NameOfCorporation.com

For example, if you wanted information about Sony products, you could look for "http://www.sony.com/". Try it!

Troubleshooting URLs

If you have trouble retrieving a file, there are several possible reasons.

URL problems
The most common reason for a URL to fail is a typo. Look at it closely and see if anything is misspelled. A URL can't contain blank spaces. The URL should end either with the name of a file or with a final /.

It's not unusual to receive an error message "404, File Not Found." This means the web server could not find a file matching that URL. Sometimes this is a temporary condition (for example, the manager of the web server may be editing or replacing the file), so try again later.

Network problems
Another common source of trouble is the network through which you are accessing the URL. The response time of a web server depends on many factors, including how busy it is, how busy the network is, and how much bandwidth is available. If a page is loading too slowly, or if you get an error message indicating that the server is too busy to accept new connections, try again later.

Sometimes your browser will report an error related to a web server's domain name. This may be a temporary problem with the name server used by your organization or ISP. The web browser relies on the name servers specified in your computer's TCP/IP software to translate domain names into a numerical form more suitable for the limited understanding of network routers. (For example, the domain name www.georgiacenter.uga.edu translates into the less catchy numeral form 128.192.37.88.) Again, try later. If domain name problems persist, ask your system administrator or ISP to help you check your TCP/IP settings.

If you're interested in a more detailed discussion of URLs, you can see David W. Baker's Guide to URLs.

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All contents copyright © 1997
University of Georgia Center for Continuing Education.
All rights reserved.

Last revised: Mon, Nov 4, 1996, 9:44:35 AM

URL: http://www.georgiacenter.uga.edu/Exploring/urls.html