This paper presents a new challenge for Web monitoring tools: to build a system that can monitor entire web sites effectively. Such a system could potentially be used to discover "silent news" hidden within corporate web sites. Examples of silent news include reorganizations in the executive team of a company or in the retirement of a product line. ChangeDetector, an implemented prototype, addresses this challenge by incorporating a number of machine learning techniques. The principal backend components of ChangeDetector all rely on machine learning: intelligent crawling, page classification and entity-based change detection. Intelligent crawling enables ChangeDetector to selectively crawl the most relevant pages of very large sites. Classification allows change detection to be filtered by topic. Entity extraction over changed pages permits change detection to be filtered by semantic concepts, such as person names, dates, addresses, and phone numbers. Finally, the front end presents a flexible way for subscribers to interact with the database of detected changes to pinpoint those changes most likely to be of interest.