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

Tap in the full name encyclopaediabritannica.com rather than the shorter britannica.com and you are taken to the “Raw Sex” site, which more than lives up to its name. Britannica’s publishers are just one of many victims of “porn-napping”, where sites are set up with an address close to a respectable organisation.

The site is then offered for sale in the hope that the organisation will be forced to buy it to prevent its 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. One geography textbook had to be reprinted after it was discovered that a website on virtual volcanoes had been replaced by raunchy material well outside the curriculum.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 does.

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.”