12. A system comprising: one or more computers; and a computer-readable medium coupled to the one or more computers having instructions stored thereon which, when executed by the one or more computers, cause the one or more computers to perform operations comprising: ranking indexed queries based on a query rank of each indexed query, the query rank calculated based on a frequency of occurrence of the indexed query and a user satisfaction score of the indexed query, the indexed queries including highly-ranked queries that are a predetermined number of queries selected based on the query rank, and nearby queries that are queries that have a statistically significant probability of being revised to one of the highly-ranked queries; calculating a respective revision score for each indexed query as a function of a revision probability of the first query and the query rank for the indexed query, the revision probability based on at least one of a semantic similarity and syntactic similarity between the first query and the respective indexed query; selecting one of the indexed queries as an alternative query to the first query based on the revision score; determining whether the alternative query is one of the highly-ranked queries or whether the alternative query is one of the nearby queries; if the alternative query is one of the highly-ranked queries, providing the highly ranked query as a suggested revision for the first query; and if the alternative query is one of the nearby queries, providing a highly ranked query that the nearby query has a statistically significant probability of being revised to, as the suggested revision for the first query.
12. A system comprising: one or more computers; and a computer-readable medium coupled to the one or more computers having instructions stored thereon which, when executed by the one or more computers, cause the one or more computers to perform operations comprising: ranking indexed queries based on a query rank of each indexed query, the query rank calculated based on a frequency of occurrence of the indexed query and a user satisfaction score of the indexed query, the indexed queries including highly-ranked queries that are a predetermined number of queries selected based on the query rank, and nearby queries that are queries that have a statistically significant probability of being revised to one of the highly-ranked queries; calculating a respective revision score for each indexed query as a function of a revision probability of the first query and the query rank for the indexed query, the revision probability based on at least one of a semantic similarity and syntactic similarity between the first query and the respective indexed query; selecting one of the indexed queries as an alternative query to the first query based on the revision score; determining whether the alternative query is one of the highly-ranked queries or whether the alternative query is one of the nearby queries; if the alternative query is one of the highly-ranked queries, providing the highly ranked query as a suggested revision for the first query; and if the alternative query is one of the nearby queries, providing a highly ranked query that the nearby query has a statistically significant probability of being revised to, as the suggested revision for the first query. 30. The system of claim 12 , wherein the suggested revision is displayed to a user in a location dependent upon a relative strength of the confidence measure.