When the search engine returns the results of a user's query they are governed by what is called the relevance score. The search engine invariably ranks first the document it believes to be most relevant based on its own parameters. As soon as you place your query, the search engine will almost instantly sort through the millions of pages and present you with ones that match your topic. The matches will even be ranked, so that the most relevant ones come first. Despite the desperate attempts by webmasters and several unethical practices people indulge in to achieve top ranking, the search engines are truly doing an amazingly honest job.
It is interesting to know how crawler-based search engines perform this daunting task of determining the relevancy of pages, sorting out millions of web pages. The search engines have a set of rules for this purpose, called algorithm and the manner it works is a well-guarded secret.
One of the principal criterion in a ranking algorithm involves the location and frequency of keywords found on a web page. Search engines will particularly check if the keywords appear right at the top of a web page, or in the headline or in the initial paragraphs of the text. It is reckoned that keyword pertinent to the topic will obviously find place right at the beginning. One more yard stick the search engine uses is to analyze how often keywords appear in relation to other words in a web page and those content which have a greater frequency are often considered more relevant than other web pages.
It is the popular belief that one of the simplest ways to improve your page ranking in the search engine results is to work on the keyword density on your page. Keyword Density is the ratio of the word that is being searched against the total number of words appearing on the web page. Assuming your keyword occurs only once in a page of five hundred words, it has a lower keyword density than a keyword that occurs four times in a page of similar word size.
If a particular keyword has a higher density on your web page, then your page is likely to obtain a better ranking. However, it should be noted that not all search engines attach importance to keyword density. Even those search engines that do have their own algorithm for computing the density of a keyword.
It has to be understood that some search engines index more web pages than others and also more often than others. Therefore, no search engine has the same collection of web pages to search through leading to differences, when comparing their results.
Search engines have the built-in check mechanism to penalize pages or exclude them from the index, anyone spamming. Search engines vigilantly looks for common spamming methods in a variety of ways and no spamming, if found, goes unpunished.
Search engines also adopt Off the Page factors for rankings as these factors cannot be easily influenced by webmasters. One of the prime Off the Page factors is link analysis. By analyzing how pages link to one other, a search engine will determine the nature of a page and whether that page is deserves a rank upgrading. Search Engines adopt advanced techniques to ward off attempts by webmasters to build artificial links to boost their rankings.
Another off the page factor is measuring the clicks. This means a search engine may watch what results a visitor selects for a particular search and based on that, downgrade high-ranking pages that are not attracting clicks and upgrade lower-ranking pages that attract more clicks.