The internet is packed full of useful information. It also provides a front for crackpots, conmen and criminals. How do you tell the good from the bad? Below are three questions that you would want to answer about the site and then links to more detailed information.

1. Who is sponsoring the site? It should be clearly stated at the top of the site's home page. Government agencies and educational institutions are likely to provide good quality information. A clue can often be found by looking at the URL ("web address"). The final letters eg .ca or .nz identify the country of origin - in these two examples Canada and New Zealand. If there is no final identifier, the site is probably American, though exceptions do exist. Preceding this will be another grouping of letters - "gov" indicates that the site belongs to a government agency and "edu" ("ac" in the UK and New Zealand) indicates that the site belongs to an educational institution such as a university. The other common suffixes "com", "org" and "net" refer to commercial entities, non-commercial organisations and networks. There is considerable variation in the types of sites with these suffixes and hence considerable variability in the quality of information provided.

2. When was the site last updated? Reliable sites will update their information regularly and the date of the last revision should be clearly stated. This is usually presented at the bottom of the page.

3. How is the material presented? Does it appear to be based on fact or is it unsubstantiated opinion? Is it presented sensationally, or is it more balanced? Factual information should be supported by references to professional literature or other web pages. Information represented as opinion should be clearly stated and identified as coming from a qualified professional or professional organisation.

For further information visit:

• DISCERN is a joint initiative of Oxford University and the National Health Service and provides a step by step guide to judging the quality of material published on the web
• A guide to critical thinking about what you see on the web.
• The University of Queensland has a guide to evaluating information on the internet.
• Monash University has a useful guide, written for its students, about evaluating resources from books, journals and the web.
• The Medical Library Association site has a useful consumers section.
• Quackwatch is an American site that provides information on a range of dubious health practices and treatments.