Classifying sites as low quality sites

A system of one or more computers configured to perform operations comprising:

• receiving a resource quality score for each of a plurality of resources linking to a site;
• assigning each of the resources 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;
• counting the number of resources in each resource quality group;
• determining a link quality score for the site using the number of resources assigned to each resource quality group, wherein determining the link quality score comprises:
• multiplying a number of resources in a first resource quality group by a first weight to determine a first product;
• multiplying a number of resources in a second resource quality group by a second weight to determine a second product;
• adding the first product and the second product to determine a sum;
• and
• determining a ratio using the sum and a total number of resources;
• and
• determining that the link quality score is below a threshold link quality score and classifying the site as a low quality site because the link quality score is below the threshold link quality score.

A computer storage medium encoded with a computer program, the program comprising instructions that when executed by one or more computers cause the one or more computers to perform operations comprising:

• receiving a resource quality score for each of a plurality of resources linking to a site;
• assigning each of the resources 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;
• counting the number of resources in each resource quality group;
• determining a link quality score for the site using the number of resources assigned to each resource quality group, wherein determining the link quality score comprises:
• multiplying a number of resources in a first resource quality group by a first weight to determine a first product;
• multiplying a number of resources in a second resource quality group by a second weight to determine a second product;
• adding the first product and the second product to determine a sum;
• and
• determining a ratio using the sum and a total number of resources;
• and
• determining that the link quality score is below a threshold link quality score and classifying the site as a low quality site because the link quality score is below the threshold link quality score.