When marketing your website, it's important to know which of your efforts are producing results and which of them are a waste of time.
You can learn a lot about this by analyzing your website's statistics (assuming your webhost offers this service).
However, even with best statistics programs, it can be difficult to determine where exactly your visitors are coming from. Did they arrive on your product page by clicking a link in your newsletter or did they get there by clicking banner you've paid to have displayed on Yahoo?
The best way to answer this question is to track your links. You can do this by buying link tracker software or by employing a third-party service to do it for you.
However, if your budget is tight, there's one way you can track your links without spending a dime.
This can be done by tagging a question mark followed by a piece of text at end of your hyperlinks. This will not affect way link works, but will help you identify that link in your website's statistics.
For example, http://www.yoursite.com/page1.htm?linka will point simply to http://www.yoursite.com/page1.htm as if "?linka" were not there at all.