Challenges for Search Engine

As the technology and the circle of web network is growing the challenges for searh engine are also growing fastly. The Web search queries one can make are currently limited to searching for keywords, which may result in many Type I and type II error positives, especially using the default whole-page search.

Better results might be achieved by using a proximity search option with a search-bracket to limit matches within a paragraph or phrase, rather than matching random words scattered across large pages. Another alternative is using human operators to do the researching for 'organic' search engine users
The Web is growing much faster than any present-technology search engine can possibly index .A web page must be reindexed each time it is changed. Dynamically generated sites may be slow or difficult to index, or may result in excessive results, perhaps generating 500 times more web pages than average.

Many dynamically generated websites are not indexable by search engines; this phenomenon is known as the invisible web. Some search engines specialize in crawling dynamic content on the invisible web that is password protected or requires forms to be filled out.

To be higher in the list of search results websites uses tricks for number of keywords. It can cause polluted results by search engine which contain little or no information matching to the keywords. And it will lead the required and relevant pages pushed down list