About Google® Search Technology:

Getting Google’s view of your site, and diagnosing potential problems
The first step to increasing your site’s visibility on Google is learning how our robots crawl and index your site.

• Crawl info: You can make sure we have access to your site, and see when Googlebot last visited. You can also view URLs that we’ve had trouble crawling and why we couldn't crawl them. This way, you can fix any problems preventing us from indexing all of your pages.
• Robots.txt file validation: See if we’re having trouble with your file, and test out changes to that file before you change it on your server.
• Website content: View top content from your site and see the words that other sites use to link to it.

Seeing how your site performs
A second step is learning what drives traffic to your site.

• Top queries: Find the top queries that drive traffic to your site and where your site is included in the top search results. This will let you learn how users are finding your site.
• Indexing information: See how your site is indexed and which of your pages are included in the index. If we find violations in your site, we’ll give you the opportunity to fix the problems and request reinclusion of your site.

Sharing info with Google about your site
Since no one knows more about your site than you do, you can also share this info with Google and improve your crawlability.

• Submit a Sitemap file: Tell us all about your pages by submitting a Sitemap file; help us learn which pages are most important to you and how often those pages change.
• Specify your preferred domain: Tell us which URL to use when indexing your site; we’ll do our best to index the version you prefer.

Google runs on a unique combination of advanced hardware and software. The speed you experience can be attributed in part to the efficiency of our search algorithm and partly to the thousands of low cost PC's we've networked together to create a superfast search engine.

The heart of our software is PageRank™, a system for ranking web pages developed by our founders Larry Page and Sergey Brin at Stanford University. And while we have dozens of engineers working to improve every aspect of Google on a daily basis, PageRank continues to play a central role in many of our web search tools.

PageRank Explained

PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page's value. In essence, Google interprets a link from page A to page B as a vote, by page A, for page B. But, Google looks at considerably more than the sheer volume of votes, or links a page receives; for example, it also analyzes the page that casts the vote. Votes cast by pages that are themselves "important" weigh more heavily and help to make other pages "important." Using these and other factors, Google provides its views on pages' relative importance.

Of course, important pages mean nothing to you if they don't match your query. So, Google combines PageRank with sophisticated text-matching techniques to find pages that are both important and relevant to your search. Google goes far beyond the number of times a term appears on a page and examines dozens of aspects of the page's content (and the content of the pages linking to it) to determine if it's a good match for your query.
Integrity

Google's complex automated methods make human tampering with our search results extremely difficult. And though we may run relevant ads above and next to our results, Google does not sell placement within the results themselves (i.e., no one can buy a particular or higher placement). A Google search provides an easy and effective way to find high-quality websites that contain information relevant to your search.