I recently started to type in the URL of a website I wanted to visit, but when I had a couple of letters typed a box scrolled down and offered the option of going to a pornographic site. Why has this happened and how can I stop it? - via e-mail.

This happens because your browser is guessing which site you are looking for based on which ones beginning with the same letters have been accessed most recently on your computer. You did not say whether you are using a computer at work or at home to use the Internet, but either way it is clear that someone other than yourself is looking at the web on the same computer.

This function is designed to make it easier for us to get to particular sites, but it can also, as you discovered, lead to offering up choices that you have no desire to visit. You can stop this from happening immediately by clearing your history list. If you are using a Microsoft Internet Explorer browser: click on tools from the task bar, then go to Internet options and click the Clear History button. Beside that there is an option to set how many days you wish to keep pages in your history. If you set it for one day you will not encounter the same problem as before unless someone else used your computer on the same day.

If you are using a Netscape browser: Go to Edit, click on Preferences and then Navigator if it has not automatically opened up there. As with Explorer, you can clear your history and set how many days you want sites to remain in your history here.

Clearing the problem is the easy part, it is finding out who went to the pornographic site in the first place that will be hard. If it was on your work computer you should consider changing your password so that no-one else can use it when you are not there. If it is your home computer, then it will probably be easier to find out who accessed the objectionable site.

The need to clear your history can also be caused by your history actually getting too full which can lead to, for example, your browser reverting to a previous day's news on a newspaper Internet site rather than the current one.

This will only happen if you are using the Internet an awful lot and you have set a very high count of days before your history is automatically cleared. If it does happen, it can be sorted out in the same way as above.