8. A non-transitory computer readable storage medium having an index structure for keyword searches stored thereon, the index structure comprising: a plurality of content words comprising single word terms and one or more biwords, the one or more biwords comprising consecutive single word terms; for each term of the single word terms and each biword of the one or more biwords, at least one document identifier containing information about a document containing the term or biword; for each of the document identifiers, at least one position identifier containing information about a section in the document containing the term or byword associated with the document identifier; for each of the position identifiers, at least one priority bit containing a priority of the term or biword associated with the position identifier, wherein a higher weight is assigned to a given term or biword matching at the position identifier with the priority bits set than at another position identifier without the priority bits set; wherein at least one of the position identifiers is a multi-bit integer of which a first plurality of bits store a section identifier associated with the respective section and a second plurality of bits store the at least one priority bit; and for each section associated with the section identifier, generating, by a processor, a content score based at least in part on a number of the terms and biwords found in the sections of each document, wherein the biwords are given a higher priority than matched terms, wherein the priority affects the content score; wherein the generating of the content score includes: counting a first total number of different terms and different biwords found in a first paragraph of the respective section, the first paragraph containing a greatest total number of different matching terms and different matching biwords among all paragraphs in the respective section; counting a second total number of different terms and different biwords found in all paragraphs of the respective section; and adding the first total to the second total to obtain the content score.
11. The computer readable storage medium as recited in claim 8 , wherein at least some of the position identifiers include a weighting value of the associated term or biword.