Internet Explorer and Firefox save a record of web sites that have been visited. If Internet Explorer isn't keeping records for long enough, click on Tools, followed by Internet Options, and move to the General tab.

Click on the Settings button in the 'Browsing history' section and, at the bottom of the dialogue box that appears, set the number of days that records should be kept for.

In Firefox click on Tools, followed by Options, and move to the Privacy section. Make sure that the box labelled 'Remember visited pages for the last x days' is ticked and enter the relevant number of days in the box before clicking on OK.