1. In a computer system comprising a user interface configured to display content items, a method for personalizing content for a particular user, the method comprising: identifying a long term profile having one or more features in a feature set and a long term level of importance associated with each term in the feature set; identifying a short term profile having one or more features in the feature set and a short term level of importance associated with each term in the feature set; identifying input related to the display of the one or more content items on the user interface; and using the input to modify the short term level of importance and the long term level of importance associated with each term in the feature set to form a modified user interest set.