Pages appear and disappear hourly. The size of the web is mammoth, and it continues to grow at an exponential rate. Search engines differ as to what percentage of the web they cover, their techniques used in obtaining coverage, and their selectivity in eliminating junk. How frequently the engine's spider crawls the web will also influence the user's choice of search tool. This is of significant importance in an age where old information is quickly superseded by the new.
All search engines support single- word queries.
The user simply types in a keyword and presses the search button. Most engines also support multiple-word queries. More specific queries will enhance the relevance of the user's results. The final step is the search, locate, and match process itself. Location and frequency of the keywords' occurrence within the document are the most common criteria used by search engines in matching and ranking.