Google's order of results is automatically determined by more than 100 factors, including our PageRank algorithm. Please check out our Technology Overview page for more details. Due to the nature of our business and our interest in protecting the integrity of our search results, we limit the information we make available to the public about our ranking system.
Each time we update our database of webpages, our index invariably shifts: we find new sites, we lose some sites, and sites' ranking may change. Your rank naturally will be affected by changes in the ranking of other sites. No one at Google hand adjusts the results to boost the ranking of a site. The order of Google's search results is automatically determined by many factors, including our PageRank algorithm, and is described in more detail here.
You might check to see if the number of other sites that link to your URL has decreased. This is the single biggest factor in determining which sites are indexed by Google, as we find most pages when our robots crawl the web, jumping from page to page via hyperlinks. To find a sampling of sites that link to yours, try a Google link search.
Google does not manually assign keywords to sites, nor do we manually "boost" the rankings of any site. The ranking process is completely automated and takes into account more than 100 factors to determine the relevance of each result.
If you'd like your site to return for particular keywords, include these words on your pages. Our crawler analyzes the content of webpages in our index to determine the search queries for which they're most relevant. If your site clearly and accurately describes your topic and many other websites link to yours, it'll likely return as a search result for your desired keywords.
If you feel that certain keywords are essential to your site's success, you may want to consider our targeted keyword advertising program. Google does not sell placement in our results, but we do offer advertising adjacent to them. Please note that advertising with Google neither helps nor hurts your site's ranking in our search results.
