The world wide web is called a web for a reason. The concept is simple. Allow people to tie (link) documents together in any manner which they see fit. This gives readers the capability to move from document to document as needed.

For example, you might have an article about diabetes which links to reports about drugs and blood monitors. These in turn may link to other documents which go into greater detail on the symptoms, as well as the results of medical studies and even FDA reports.

This is the way the web was designed to work. When a document (an HTML page) is properly designed, it references sources all over the web as needed for many different reasons:

- to go into greater detail on the subject matter - to provide alternate viewpoints - to give supporting evidence - to provide references used in the creation of the document - to list additional related information - to define terms

Properly used and maintained, external links add incredible value to a web site. Some webmasters do not like to include any external links (except for those carefully segregated on a "links page") because they believe that this causes visitors to leave their site. Their belief is they worked very hard to get people to visit, so why encourage them to leave?

These webmasters do not really understand the web. Furthermore, they do not comprehend the major reasons why people visit sites in the first place, and why they return to the same site over and over.

As a rule (with some exceptions) people surf the web because they are looking for information or entertainment. These are the primary uses of the internet. Generally, surveys show that shopping or making any kind of purchase is not high on the reasons people spend their time web surfing. No indeed, what they primarily want is to find out something. In fact, it is quite common for your average surfer to use a web site to research their purchase, then drive down to the local store to pick it up themselves.

If you site has a good, well coordinated set of external links than you are giving your visitors access to additional information, which in turn provides them with an excellent reason to visit your site again. Yes, your visitor may surf elsewhere, but given that the quality of the external links is high, he will most likely return.

I have spent much time figuring out a good ratio of external links within a web site. I have found that a site can definitely have too many links to other sites. Too many links produces a whole series of problems:

- The internet is very active, so links tend to become obsolete very quickly. If you have a very large number of links in your site, you are ensuring that you will spend a great amount of time checking for link rot (http://www.internet-tips.net/Webmaster/maintlinkrot.htm). If you do not check your links often more and more of them will produce 404 errors, which will tend to cause visitors to NOT return to your site.

- The desire is to have quality links. This is what causes visitors to want to return. A large quantity of external links (especially a huge number on a single page) tends to make it seem as if the links are of lesser quality. In other words, the appearance is that you just slapped together a bunch of links without much thought.

- If a large number of your links are of subjects unrelated to your web site, then you most definitely have degraded, in the eyes of your visitors, your site. You see, they came to your site because it contained information about a specific subject (or several different subjects). Linking to unrelated sites tends to dilute your site and chase away visitors.

Too few external links tends to make your site look small and uninviting. People enjoy the choices associated with the web, and a site which has no external links feels cramped and confining. It's kind of like being in a building without any windows. I believe it tends to create an atmosphere where people want to rush in, get what they want and leave, never to return.

The best sites present an external link here and another one there. Perhaps two or three well-picked references at the end of an article are appropriate. Also, sprinkling an appropriate link to well-written reference or two within an article is an excellent idea. These kinds of things can strengthen your writing and make it more powerful. For example, if you have written an article about asthma, including a few references (within the text) to other pages which strengthen your arguments tends to make your own arguments stronger and more believable.

Normally I do not like popup windows. However, when linking to external sites the best way to keep visitors from leaving is to simply pop up a new window anytime an external link is clicked. This allows your visitors to surf the external site to their hearts contend. When they are finished and close the window, your site is still up and waiting for them. Thus, I've found that popup windows are fine for external sites which present additional data - they are not okay for advertisements or promotional materials.

One annoyance that I've found in some sites is affiliate links which are camouflaged as links to valid external sites. I don't mind people making money on the internet, but please don't try and fool me into clicking on something so you can make a few pennies. Honest businesspeople tend to produce return customers - dishonesty might make a few pennies in the short term but will cause people to never return.

What do I mean by this? It's okay, say, to include a link to the amazon.com page with a book related to the subject as long as it is labeled as such. You might say, "The book 'blah blah' helped me overcome my asthma" with "blah blah" an affiliate link to amazon.com. From the text, people can expect that they will be presented with a way to order the book. However, making that same link appear as a reference in your writing ("asthma is a disease which causes shortness of breath" with "asthma" hyperlinked with an affiliate link to a book, for example) is being slightly dishonest with your visitors. People click on the link expecting to get some information, and instead they find an order form ... this tends to cause them to (a) not buy the thing, and (b) surf somewhere else. You are not delivering what you promised to deliver.

There are places on a web site in which masses of external links are not only necessary but desired. A links page is a perfect example of this practice. This is the concept of including a list of several dozen related links on one or more pages. The only purpose of the pages is to link to sites with related subjects.

Other good examples include free-for-all links pages, link exchange pages and portal pages. As long as the links are related in some way to the subject matter of your site, you will be adding value for your visitors and thus encouraging them to return in the future.

In summary, external links are very important to creating a web site which encourages people to return again and again. However, you must be careful to ensure your links are well chosen and of subjects related to your site's subject - otherwise, you will be giving your visitors excuses to leave without returning.