This is an edited version of an item in Nick Renton's Enjoy your English!

Many books and other publications include references to links to various web sites which contain information likely to be of interest or relevance to their readers. Often the data on these sites will be updated periodically - an important advantage over the contents of a printed work.

However, one problem is the ephemeral nature of the Internet. Some web addresses get changed over time, while in other cases the pages are simply removed. Some addresses are rather long, increasing the scope for typographical errors which render the link completely useless. Manual checking can be time-consuming and tedious.

One solution is for the author to put all the links into a single appendix. This appendix can then be uploaded to an appropriate web site. Once there the validity of all links can very quickly be checked electronically by using http://www.siteowner.com/badlinks.cfm.

Any annoying "404" errors ("page not found") can then be investigated and rectified.

However, it should be noted that this method is not foolproof. For example, it will not report as missing any pages which still have valid addresses but which show messages to the effect that the site concerned has been shut down.

Naturally, a final check should be carried out at the last possible moment before the publication concerned goes to the printer.