The multimedia information retrieval community has dedicated extensive research effort to the problem of content-based image retrieval (CBIR). However, these systems find their main limitation in the difficulty of creating pictorial queries. As a result, few systems offer the option of querying by visual examples, and rely on automatic concept detection and tagging techniques to provide support for searching visual content using textual queries. This paper proposes and studies a practical multimodal web search scenario, where CBIR fits intuitively to improve the retrieval of rich information queries. Many online articles contain useful know-how knowledge about computer applications. These articles tend to be richly illustrated by screenshots. We present a system to search for such software know-how articles that leverages the visual correspondences between screenshots. Users can naturally create pictorial queries simply by taking a screenshot of the application to retrieve a list of articles containing a matching screenshot. We build a prototype comprising 150k articles that are classified into walkthrough, book, gallery, and general categories, and provide a comprehensive evaluation of this system, focusing on technical (accuracy of CBIR techniques) and usability (perceived system usefulness) aspects. We also consider the study of added value features of such a visual-supported search, including the ability to perform cross-lingual queries. We find that the system is able to retrieve matching screenshots for a wide variety of programs, across language boundaries, and provide subjectively more useful results than keyword-based web and image search engines.