1. A ranking system comprising: a memory comprising at least one negation term; a processor comprising: a document ranking application comprising modules executable by the processor to process a plurality of documents retrieved from a data source, the document ranking application comprising: a token generation module to generate a corresponding token for each word in document data included in at least one of the plurality of documents; and a tagging module to: retrieve the at least one negation term and at least one negation rule from the memory; compare the at least one negation term according to the at least one negation rule to other terms in the document data that are within a selected proximity of each word; assign a negative tag to the corresponding token for a particular word if the at least one negation term matches any other terms within the selected proximity of the particular word according to the negation rule; assign a positive tag to the corresponding token for the particular word if the at least one negation term does not match any of the other terms within the selected proximity of the particular word according to the negation rule; and store processed document data for the at least one document in a data store, the processed document data comprising document content, tokens, and the tags assigned to each of the tokens; a document data display application comprising modules executable by the processor to generate processed document data for display in response to a search request, the document data display application comprising: a token analysis module to: receive the search request including document identification data; identify the processed document data in the data store that corresponds to the document identification data; and search the processed document data for tokens that have been assigned the positive context tag; and a display module to generate the processed document data for display that includes visual indicators for each word where the corresponding token is assigned the positive context tag.