1. A computer-implemented method comprising: under control of one or more computer systems configured with executable instructions, generating a set of signatures for a plurality of electronic documents by at least in part determining one or more codes each of which represents a unique portion of a selected content from the plurality of electronic documents, wherein the unique portion of the selected content is associated with a particular set of characters different from other sets of characters in the selected content, and wherein each of the one or more codes includes a hash that is generated based on utilizing the unique portion of the selected content as input in order to output the hash, the hash being generated as an identifier for the unique portion of the selected content, wherein each signature in the set of signatures is formed at least in part by a set of hashes; generating an index that associates the one or more codes for a signature with a document location unique to a corresponding electronic document; and upon determining that a received document location and a received signature for a requested electronic document is invalid: identifying two or more electronic documents from the plurality of electronic documents, each of the two or more identified electronic documents having a respective plural number of codes that match at least a subset of a plural number of codes of the received signature; and providing two or more links each specifying a respective location corresponding to a respective one of the two or more identified electronic documents, the respective location being determined according to the index and being different than the received document location, the two or more links being ordered according to a percentage of matching between the respective plural number of codes of each identified document and the plural number of codes of the received signature, the percentage indicating an estimate of an adjustable threshold amount of content associated with the received signature that will be included with each of the two or more links.