A change-detection web server automatically checks web-page documents for recent changes. The server retrieves and compares documents one or more times a week. The user is notified by electronic mail when a change is detected. The user registers a web-page document by submitting his e-mail address and...http://www.google.com.hk/patents/US5898836?utm_source=gb-gplus-share專利 US5898836 - Change-detection tool indicating degree and location of change of internet documents by comparison of cyclic-redundancy-check(CRC) signatures
