URLs provide a standard format for the transmission and reception of a wide variety of information types. Here is how they are constructed:
transfer protocol://servername.domain/directory/subdirectory/filename.filetype
The First part: Transfer protocol
The first part of the URL indicates what type of information is being transferred and, usually, what port (or "door") to the server is being accessed. Here are the most common types:
The Second part: Servername.domain
When you perform a simple yet elegant click of the mouse, your Web browser goes into high gear. It sends a message to a server, or computer where a Web site resides, asking it to send you information. The transfer protocol tells your computer and the server what formats of information need to be interpreted and with what particular features (e.g., I am using Lynx, so please don't send me images). The servername.domain is the address of the server itself: your message has to go somewhere. Most server addresses have three parts:
Most servers have a name of some kind. It is a fallacy that all Web servers are called "www." Many are, but that is a simple matter of choice. Look at the URL of the document you are reading: you're looking at it on the Web, and there is no "www" in it's name. The domain is key to understanding where the information is coming from. Is it an educational institution, or is it a commercial service such as Prodigy or AOL? This is an important consideration when you are trying to evaluate an electronic document. Don't forget, the Internet is vanity publishing on its largest scale. This doesn't mean that documents coming from someone's personal commercial account are not valuable: it means that you have to apply your critical thinking skills.
For the U.S., these are the following classes of Internet domains:
The Third part: Directories and subdirectories
Once you have been admitted to a server to get a document or "page", you need to know where you're going. Servers act just like your home computer: you keep your word-processing program in a separate directory from your modem software. In fact, your computer probably keeps the word processing documents in a separate subdirectory in the word-processing directory. Computers need to be neat and tidy in order to run efficiently. This is even more true when the computer is sending billions of bytes of information all over the world. The third part of the URL takes you directly to the directory and subdirectory where the page you want lives.
Here are examples of URLs pointing to directories and subdirectories:
The default document name that all browsers search for in any directory is "index.htm" or "index.html". If no specific file name is entered, the browsers search for the "index" file. If not found, an error message, the famous "404 - document not found" is displayed. This means that all directories and subdirectories should have, at a minimum, an "index" file.
The Fourth part: Files and file names
While any file will technically work on the Internet, there are a small number of file types that comprise almost 100% of the files in use. These file naming conventions have become "standard" because they convey the types of information in the files.
The most common file is the "html" file. This is the text file that contains the text information displayed on the screen. "filename.html" is a file name example. People with older computers will often create "htm" files, and they are the same as "html" files.
Two types of graphic picture files formats work on the Internet: "jpg" and "gif". If you download (steal) pictures from the Internet you need to note the file type. Be sure to save the scanned pictures of the grandchildren as either "jpg" or "gif" files.
"zip" files are files that have been "zipped," or compressed into a smaller size to facilitate transmission. You will need a zip/unzip program to prepare and to read them. PKZip is the most popular of the compression programs. A free trial copy can be downloaded from the PKWare web site.
As I mentioned, any file format and name will work, but staying with these naming conventions will assist you when working with Internet files.
Here is the link to URL Information.
This link takes you to a site that discusses the importance of URLs for businesses.