1. A method of evaluating trust of a target web document present in a web environment which comprises a plurality of web documents, the method comprising: defining a plurality of trust attributes for the target web document, the plurality of trust attributes being categorized in a first category which relates to contents of the web document, a second category which relates to owner of the web document, and a third category which relates to relationships of the web document and certificate authorities; obtaining trust attribute values of at least some of the trust attributes; calculating a P value representing a standalone page trust assessment of the target web document based on trust attribute values in the first category; calculating a Q value representing a standalone page trust assessment of the target web document based on trust attribute values in the second and third categories; calculating an S value representing a subordinate node assessment, based on a total trust value and a relevance value R of each of a plurality of other web documents linked to the target web document; and calculating a total trust value of the target web document based on the P, Q and S values.