1. A method in a computing device that is programmed for ranking documents with links between the documents, the method comprising: providing a first document graph representing links between the documents at a first time and a second document graph representing links between the documents at a second time that is later than the first time; determining by the computing device a first ranking of the documents based on the first document graph by: initializing a first jumping vector indicating probabilities of visiting the documents without using a link, the initializing including setting the probability of visiting a suspected spam document without using a link to zero; and generating a first transition probability matrix indicating probabilities of visiting the documents using links; and applying a page ranking algorithm to the first document graph to generate a first ranking of the documents based on the first transition probability matrix and the first jumping vector wherein the ranking of the suspected spam document is lowered as a result of setting the probability of visiting the suspect spam document without using a link to zero; and determining by the computing device a second ranking of the documents based on the second document graph and the first ranking of the documents based on the first document graph by: initializing a second jumping vector indicating probabilities of visiting the documents without using a link, the second jumping vector being initialized based on the first ranking of documents such that a higher first ranking increases the probability of visiting a document without a link; and generating a second transition probability matrix indicating probabilities of visiting the documents using links; and applying a page ranking algorithm to the second document graph to generate a second ranking of the documents based on the second transition probability matrix and the second jumping vector.