1. A method comprising: receiving, by at least one computer, crawling data from a crawler crawling a content preview source; extracting, by the at least one computer in connection with crawling the content preview source, data and a link from the content preview source, the link comprising a link to a target document, the data to be used to create a content preview document previewing the target document, the target document containing content being previewed by the content preview source; creating, by the at least one computer in connection with crawling the content preview source, the content preview document using the data extracted from the content preview source, the content preview document being different from the target document and the content preview source, the content preview document being created without using the target document; and making, by the at least one computer, the created content preview document available for searching by a search engine in an index prior to the target document being made available for searching by the search engine in the index.
1. A method comprising: receiving, by at least one computer, crawling data from a crawler crawling a content preview source; extracting, by the at least one computer in connection with crawling the content preview source, data and a link from the content preview source, the link comprising a link to a target document, the data to be used to create a content preview document previewing the target document, the target document containing content being previewed by the content preview source; creating, by the at least one computer in connection with crawling the content preview source, the content preview document using the data extracted from the content preview source, the content preview document being different from the target document and the content preview source, the content preview document being created without using the target document; and making, by the at least one computer, the created content preview document available for searching by a search engine in an index prior to the target document being made available for searching by the search engine in the index. 12. The method of claim 1 , further comprising: selecting the content preview source from a plurality of content preview sources using a quality measure determined for the content preview source.