Have you checked your server log lately?

If you maintain a worldwide web, Gopher, or FTP site or you use an auto-responder to distribute e-mail documents, the server that handles your presentation maintains a log that can be valuable to you. It shows how many different computers access your files each day, and which network domains those requests come from. If you're using an auto-responder program, the log also shows the e-mail address of each person who asks for the information being distributed. Ask your service provider to send you a copy of your server log once a month, and then monitor them to determine whether your traffic is increasing or decreasing, which of your web pages are most popular, and who is receiving documents from your auto-responder.