Embodiments of methods and apparatuses for searching contents, including structured search are described herein. Embodiments of the present invention use tree structures (or more generally, graph structures), layout structures, and/or content category information to capture within search results relevant content that would otherwise be missed, to reduce the incidence of false positives within search results, and to improve the accuracy of rankings within search results. Embodiments of the present invention further use tree structures (or more generally, graph structures), layout structures, and/or content category information to extend search results to include sub-document constituents. Embodiments of the present invention also support the use of distribution properties as criteria for ranking search results. And embodiments of the present invention support search based on structural proximity, search expressions with recursively embedded operators, predicates, and/or quantifiers, and applications to selection of advertisements.