Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for enhancing search results. In one aspect, a method includes receiving a resource quality score for each of a plurality of resources linking to a site/ Each of the resources is assigned to one of a plurality of resource quality groups, each resource quality group being associated with a range of resource quality scores, each resource being assigned to the resource quality group associated with the range encompassing the resource quality score for the resource. The number of resources in each resources quality group is counted. A link quality score is determined for the site using the number of resources in each resource quality group. If the link quality score is below a threshold link quality score, the site is classified as a low quality site.
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