One exemplary aspect comprises a computer system comprising: (a) a preprocessing unit that extracts text from a webpage to produce at least a first set of candidate keywords, applies language processing to produce at least a second set of candidate keywords, and combines said first and second sets of candidate keywords into a first candidate pool; (b) a candidate extraction unit that receives data from said preprocessing unit describing at least said first candidate pool and produces a second candidate pool; (c) a feature extraction unit that receives data describing at least said second candidate pool and analyzes said second candidate pool for general features and linguistic features; and (d) a classification unit that receives said data describing at least said second candidate pool and related data from said feature extraction unit, and determines a likelihood of each candidate in said second candidate pool being a primary or secondary keyword.