I've been hearing that something called "cookies" can be used to trace you on the Internet. What are cookies? - Brian O'Keeffe, Co Kerry

Most commercial websites attach a cookie file to you when you visit their pages. There are many theories as to where the name comes from, but my own suggestion is that it is based on the Hansel and Gretel fable, where the two children used a trail of crumbs in order to find their way back out of the forest. This is very similar to how cookies work. It is a connection between the sites you see and your computer.

Cookies were originally designed as a way of making it easier for users to access their favourite websites without having to go through a long process of identification each time they go to a particular site. It is, for example, how amazon.com knows to greet you by name when you go to their site, and how they can make personal recommendations based on your previous purchases.

However, according to information technology consultant Kevin Smith, cookies can also lead to receiving e-mail messages from undesirable places. "Cookies store a certain amount of information on you, such as which sites you access. If, for instance, you have looked at a pornography site, inadvertently or otherwise, cookies can pick up your e-mail address and they may bombard you with e-mails looking for your credit card number and asking you to sign up to their service."

It is possible to turn off the cookies option on your computer, but there are a lot of sites that will not allow you access unless your cookies are switched on.

If you are using a Netscape browser, you can turn off your cookies by clicking on the edit button on your toolbar. From there you go into "preferences" and then into "advanced". From there it is simply a case of clicking on the "disable cookies" option. You can alternatively ask to be warned if cookies are required to visit a particular location.

For details on how to turn off cookies in other types of browsers, go to www.cookiecentral.com. This site will also automatically tell you whether or not the browser you are using supports cookies. It is worth noting that nearly all the most modern types of browsers do.

In the main cookies are a useful invention which makes navigating the web easier.

Send your WebWorld queries to pcollins@irishtimes.com or by post to Padraig Collins, The Irish Times, D'Olier Street, Dublin 2.