Create a basic secure area within a website

Create a basic security system which requires users to enter a username and password to view the contents of a HTML page. There is no SSL certificate involved so it needs to work on http: pages and provide some degree of security. The username and password will be standardised, i.e. there is only one username and password. This will allow certain users access to an area of a website. This system will need to be easily replicated by the website manger to other future websites and to have the username and password changed accordingly.