HTML and CSS Reference
This search algorithm does a remarkably good job of pushing the most relevant sites to
the top of the search results. It also rewards people who publish useful, popular sites
rather than those who've figured out how to manipulate the algorithms that other search
engines use. Many sites that aren't dedicated to providing search functionality use
Google's index, so getting into the Google index provides wide exposure. As of summer
2010, Google's share of the search engine market is 65%.
How Search Results Are Ranked
Every search engine has an algorithm that ranks sites based on their relevance. It
might take into account how many times the keyword you enter appears on the
page, whether it appears inside heading tags or in the page title, or whether it
appears in text inside links. It might also take into account how high on the page
your search terms appear. Such algorithms are trade secrets within the search
engine industry, but some of them have been unraveled to greater or lesser degrees.
Armed with this information, some site authors write their pages in such a way that
search engines will give them a higher relevance ranking than they deserve. For
example, some sites have long titles with lots of information in hopes of appearing
first in search results.
Yahoo! has been around since 1994. It provides both a human-edited directory of the
Web, which I discussed earlier, and web search. Yahoo's search engine currently uses its
own index, but it has an agreement with Microsoft to use the Bing index at some point in
the future. Yahoo!'s share of the search engine market is around 17% at the time of this
Bing is Microsoft's web search offering. Like Google, Microsoft maintains its own index
of the Web. Bing was launched in May 2009, and as of May 2010 had an 11% market
share among search engines.
Ask.com is another search engine that maintains its own index. Ask.com indexes fewer
pages than Google or Yahoo! Ask.com controls only about 2% of the search engine mar-
ket as of summer 2010, but is listed because, like the other sites listed previously, it has
its own index.