Search engine optimization different signals. The leading search engines, Google, Bing, and Yahoo, do not disclose the algorithms they use to rank pages. Some SEO practitioners have studied different approaches to search engine optimization, and have shared their personal opinions. Patents related to search engines can provide information to better understand search engines. In 2005, Google began personalizing search results for each user. Depending on their history of previous searches, Google crafted results for logged in users. In 2007, Google announced a campaign against paid links that transfer PageRank. On June 15, 2009, Google disclosed that they had taken measures to mitigate the
Microsoft Search Server to extract the text of the file for full text indexing as well. The handlers and iFilters MSS uses are the same as used by SharePoint, Microsoft SQL Server and Windows Search as well. The data sources that are to be indexed are identified by their URIs and have to be configured prior to indexing. The indexer updates the search index as soon as an item is indexed ("continuous propagation") so that the items can be queried against even before the indexing crawl is complete. MSS can also federate searches to other search services (including SharePoint and web search servers)