Systems and methods for applications of orthogonal corpus indexing (OCI), such as selecting ad words for purchase and improving visibility of web pages in search engines, are described. In one aspect, the systems and methods described herein employ OCI to recommend to an advertiser ad words for purchase. Advertisers pay search engines for placement of their advertising along side results in the search results page, when a given word or phrase appears in a user's search query. The described systems and methods enable automated selection of related and discriminating terms, identifying keywords that increase the ratio of ads clicked-through to money spent on keyword buying. In another aspect, the systems and methods described herein employ OCI to generate content for web pages. OCI may be used to determine content that when added to a web page improves the rank of that page in a search engine.