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As discussed earlier, Hyperlinks are those elements of HTML which makes it possible for us to navigate through different web pages or to different locations within a single web page. They are also used for adding e-mail support in the HTML document. In fact, hyperlinks act as the backbone of a website. As these links are used to fulfill different types of needs and demands, the way they are defined in the HTML document varies according to the circumstances. Every hyperlink needs an address to the location where the hyperlink is intended to redirect us. Technically speaking, each hyperlink needs a URL in order to point towards another location. External hyperlinks points towards a webpage of a different website on the same web server, whereas internal hyperlinks point towards a location on the same web page or to a different webpage of the same website. He structure can be more complex if a hyperlink is intended to point towards a web page of different website on the different web server. In each of the cases the way a URL is defined differs. It is very important to understand and learn the different ways to write the URLs because each type of URL changes the meaning of the hyperlink. The syntax of the URLs decided whether a hyperlink is internal, external or it is an e-mail link. Below are some examples of most common ways to write the URLs, each changing the intended meaning of the hyperlink.

1) <A NAME=”bottom”>Bottom</A>

<A HREF=”#bottom”>Go to bottom</A>

This is an internal hyperlink which is redirecting the user at the bottom of the same web page which he is currently viewing. To make this hyperlink an internal one, note the way the URL is written after the HREF attribute of anchor tag. There is no file name or path to a file name before the # sign. This makes the hyperlink an internal one.

2) <A HREF=”welcome.html#hi”>

This is an example of a hyperlink which redirects to a different document of the same folder. This means that both the linked documents are contained under the same parent folder.

3) <A HREF=”hello/welcome.html#hi”>

This is a hyperlink which points towards a different document residing in a different folder. But, in this case both the folders whose web documents are linked with each other are on the same web server.

4) <A HREF=”http://www.yahoo.com/good/hello/welcome.html#hi”>

The above example represents a hyperlink which is pointing towards a different web document which resides in a different folder on a different web server. This makes the hyperlink completely an external one.

5) <A HREF=”mailto://queries@content mantra.com”>

This type of URL consisting of ‘mailto:’ protocol indicated that the hyperlink is linked to a mail server.

So, the way URLs are used, changes the purpose and functioning of the hyperlinks. In fact, how much information you should include in the URL of a hyperlink depends upon where the hyperlink is redirecting the user i.e. where the linked resource is is located.

URLs (Uniform Resource Locators) are the addresses of all the links and resources which are globally hosted on the World Wide Web. A web page address like http://www.yahoo.com is a URL. It takes you to the home page of yahoo. Whenever you click on a link on a web page, it takes you to another web page. Technically speaking it redirects you to a new URL. Therefore we can say that every hyperlink is associated with a URL. Generally what we type in the address bar is like yahoo.com and then the Yahoo website opens in our web browser. It does not show any errors because the DNS resolves yahoo.com in its full format automatically. Actually yahoo.com is not the complete URL. A complete URL consists of different sections each indicating important information about the web page.

Let us take a comprehensive example of a URL such as

http://www.3seas.com/html/introduction.htm.

This URL has different sub sections which are described below:

1. Scheme: It defines the type of protocol which has been used in a particular URL. For eg; the http is the scheme which defines the type of internet service used.
2. Host: It defines the domain host. The default host for http is www
3. Domain: It defines the domain name which has been registered online. 3seas.com is the domain name.
4. Port: It defines the port number on which the http service is running. It is not displayed in the URL.
5. The default port number for http is 80. However, this port number can be changed by the IIS administrator.
6. Path: It shows the complete path of the directory located at the web server.
7. File Name: It tells the name of the document whose contents are being displayed on the screen. In our example, introduction.htm is the file name.

Thus, technically we can split a complete URL as:

scheme://host.domain:port/path/filename

The domain part of the URL can also be split into logical parts. In http;//3seas.com/html/introduction.htm, The 3seas.com is the domain name out of which 3seas defines a unique entity on world wide web (also known as 1st Level domain). The .com represents the top level domain. This is used to describe the type of website. There are predefined standards which indicate the top level domains and their corresponding meanings. Some of the popular ones are:

COM It shows that the web page is intended for commercial business
2) .ORG It represents a non commercial community website
3) .NET This is used by ISPs (Internet Service Providers)
4) .MIL It is used by Military of United states only.
5) .GOV Used only by government agencies

Apart from the top level domain and 1st level domain, a domain name can also have various sub domains arranged in a hierarchy. All of them are separated by a period ‘.’ The left most represents the lowest level in domain hierarchy and the rightmost represents the top level domain. A typical example of domain name hierarchy is:

www.india.asia.nokia.com

Where india represents the lowest level in the domain hierarchy and .com represents the top level domain.

In HTML coding the URLs to a link are defined with the help of <a> tag. For eg:

<a href=””http://www.yahoo.com””>Click Here</a></p>

According to the above example you will be redirected to yahoo.com if you click on Click Here text on the web page. Although you will not find any difference whether you type the URL in upper case or lower case because the DNS server resolves that automatically, but it should be noted that the URLs are always case sensitive.