Eugene's observations

A client of mine has run into problems with Ocado - a website that collects orders for grocery deliveries ordered online. Their technical support people advised that she delete all her cookies to see if that resolved the issue. When you are advised to do this it is a sure indication that the person offering such advice has no idea of the cause of your problem, and, whether through ignorance or careless disregard for your convenience, no interest in the consequences when you visit other websites.

A cookie is a small file that many websites cause to be placed on your computer when you browse to them. They are usually helpful as they record information that you would want the website to know, gleaned from your previous visits to their site.

Cookies may be used to remember and thus save your having to re-type in your username or password. To remember what was in your shopping cart, your preferences, or the state of what you were doing before you had to leave the website last visit.

Occasionally however, third party websites can harvest information held in other website's cookies with a view to targeting marketing at you or stealing information you may regard as confidential to a particular website. The sites that allow collection of this material for advertisers are called adservers, and their cookies are usually best deleted. This is often automated in most anti-spyware programs (e.g. Spybot, Ad-Aware & SUPERAntiSpyware).

The possible problem that affected my client, the Ocado site user, was a corrupt cookie. It is just possible that the Ocado site wrote a cookie that later became corrupted - possibly due to hard disk drive error, virus activity or simply being badly written by Ocado in the first place ! Further, that the Ocado website code was written in a way that it could not handle this eventuality. In such a situation, deleting all OCADO cookies may be helpful. But advising my client to delete all cookies for all websites on the computer is recklessly bad advice.

To view and/or selectively delete cookies from multiple browsers, I use a program called Cookie Viewer - a free download from http://www.karenware.com/powertools/ptcookie.asp

Another useful free program is Cookie Monster. It combines cookies from multiple browsers and makes it easy to delete cookies not relating to sites in your favourites/bookmarks list. Available from
http://www.ampsoft.net/utilities/CookieMonster.php

More information on cookies is available at Wikipedia.