A CGI script to show the number of visitors to your website within the past X minutes, hours or days. If the SSI tag is only placed at the main page of the website, it displays: "There were X visitors reaching this page since the past Y minutes". If the tag is placed on every page and Y is set to 1 minute or lower, then it would be quite accurate to say (since the date/time is updated on every reload): "There are currently X unique visitors at this website".