1. One or more computer storage media encoded with a computer program for use in conjunction with a computer system, the computer program comprising instructions that when executed by data processing apparatus cause the data processing apparatus to perform operations, the operations comprising: generating an updated sitemap mapping document that represents an organization of related network-accessible documents within a website; making the updated sitemap mapping document available for access; and in response to the making the updated sitemap mapping document available, transmitting to a remote computer a notification that includes an indication that the updated sitemap mapping document is available and an indication that at least some of the network-accessible documents whose organization is represented by the updated sitemap mapping document are mobile content.