13. The one or more computer systems of claim 11 , wherein the category is determined through a process, wherein the process includes one of the following: simple prediction, smoothed browse node prediction, expanded query group, N-Gram generative model, estimated probability as prior, or interpolation between multiple prediction models.
13. The one or more computer systems of claim 11 , wherein the category is determined through a process, wherein the process includes one of the following: simple prediction, smoothed browse node prediction, expanded query group, N-Gram generative model, estimated probability as prior, or interpolation between multiple prediction models. 17. The one or more computer systems of claim 13 , wherein the interpolation between multiple prediction models uses a formula: 
 P (Click x |Q )=Σλ n P n (Click x |Q ) wherein P is a probability, Click x is an observation of a click in browse node x, λ n is learned parameters, and P n (Click x |Q) is a probability of click given the search query.