An interesting site run by Netcraft offers a range of services in the areas of World Wide Web Publishing, Internet Security, and Contract Systems & Network Management. In particular, you can use their online software to find out about how an external site is running or is configured. This sort of information is useful for those with a technical interest in site building and maintenance

Netcraft has developed a service which examines a network connected to the Internet and reports back to you which hosts are visible and what protocols and services they make available to the Internet at large. It then probes the available services for vulnerabilities including misconfigurations and erroneous software versions. Access to information analysing the vulnerabilities and support by internet mail are included as standard.