But beware. Get the site name slightly wrong and your class of seven-year-olds could be confronted by explicit pornography.

Those who tap in the full name encyclopaediabritannica.com rather than the shorter britannica.com are taken to the “Raw Sex” website, which more than lives up to its name. Britannica’s publishers are just one of many victims of “porn-napping”, a practice where porn-peddlers set up a site with an address close to a respectable organisation. They then offer the site for sale in the hope that the organisation or someone else will buy it to prevent the name being tarnished.

“This is something we will be looking into as a matter of urgency,” a Britannica spokesman said. “While we have registered a number of common misspellings and redirect people who enter those addresses to our site, we obviously can’t register every possibility.”

Websites for schools and young people are particularly vulnerable to this sort of abuse. One key stage 3 geography textbook had to be reprinted recently when it was discovered that a website orginally devoted to virtual volcanoes had been replaced by raunchy material well outside the curriculum.

And young pop fans who miss out the “e” from the first name of Britney Spears will see women wearing even fewer clothes than the teen idol usually does. Other seemingly educational sites, such as “civil war battles”, “the internet education group” and “the music education directory” also lead to porn.

The problem is causing increasing difficulty for all educational publishers. Honor Wilson-Fletcher, sales and marketing director at Hodder Children’s Books, said: “Like most educational publishers, we have increasingly been adding web-links to our publications, but we are no longer willing to do this because we may inadvertently end up advertising porn sites.

“Parents, teachers and all those who work with children need to be on their guard.”