14. A method of presenting search results using an anchor stream generated by propagating terms between documents that are related by hyperlinks, the method comprising: receiving a search query comprised of one or more terms; determining that a target document matches the search query because at least one term of the one or more terms is associated with the target document in an anchor stream, wherein the anchor stream associates terms that are not included in the target document with the target document because the terms are included in a related document and determined to be relevant to the target document, and wherein the related document is linked from the target document; determining that the target document matches the search query because the at least one term of the one or more terms is associated with the target document in a signal stream, wherein the signal stream associates terms that are included in the target document with the target document; and presenting the target document as a search result that is responsive to the search query.
14. A method of presenting search results using an anchor stream generated by propagating terms between documents that are related by hyperlinks, the method comprising: receiving a search query comprised of one or more terms; determining that a target document matches the search query because at least one term of the one or more terms is associated with the target document in an anchor stream, wherein the anchor stream associates terms that are not included in the target document with the target document because the terms are included in a related document and determined to be relevant to the target document, and wherein the related document is linked from the target document; determining that the target document matches the search query because the at least one term of the one or more terms is associated with the target document in a signal stream, wherein the signal stream associates terms that are included in the target document with the target document; and presenting the target document as a search result that is responsive to the search query. 18. The method of claim 14 , wherein the anchor stream is a forward-looking anchor stream that associates terms from a different document, which is linked from the target document, with the target document.