Firstly its my concern to remind you that search engines are just a program to search desired data according to given instructions in its algorithm. It can’t behave like human being. And the major difference to view web pages is varies between human and search engine. Search engine cannot be impressed by looks, pictures, flash and videos. The only attraction for it is content, Or we can say that the search engine is very much hungry of new content. Whenever we talk about humans they always attracted by outer views like layout, pictures etc.
Now we have an idea about search engines, that they are text-motored. Though technology changing rapidly everyday, it may be possible in near future search engine would enjoy & recognize web clips, sounds and layouts. In real web world search engines go through the Web, and searching at particular website content mainly text to get an idea what website is about. Search engines are involved to perform various activities to show us better search results i.e. crawling the web, indexing of web pages, processing of them, calculation of relevant content, and retrieving the information from database in order to fulfill user needs.
Google and other major search engines have a software program called crawler or spider that crawls the web, It keeps an eye on links from one web page to some other and index them all are coming in their way. Although billions of web pages are there so that its impossible to crawl every page every day. It happens sometime that your page isn’t cached for a long time, but don’t be keep quiet in waiting to be cached, do some SEO.
When it comes to the indexing of web page after crawling, search engine has a very large database to index its content, from where it can be retrieved later. Depend on your keyword, title and description given in Meta tags. Sometimes it happens that search engine is unable to categorize or classify your content for that you have to optimize your site for targeted keywords.
After all when some one enters a keyword phrase to search information, search engine process keyword to match with related pages and checks its relevancy and show results in SERP. All Search engines have their algorithm to find relevancy of content depends upon keyword density, age of URL, back links and Meta tags. That’s why every search engine gives different search result. Because all search engines are modifying their algorithm time to time so that it becomes necessary to do SEO efforts continuously.
Although the basic principle of operation of all search engines is the same, the minor differences between them lead to major changes in results relevancy. For different search engines different factors are important. There were times, when SEO experts joked that the algorithms of Yahoo! are intentionally made just the opposite of those of Google. While this might have a grain of truth, it is a matter a fact that the major search engines like different stuff and if you plan to conquer more than one of them, you need to optimize carefully.
The basic formula for indexing is to have unique content for all search engines. Preferences vary one to another but I want to tell you one more thing that google likes links and the old domains, others haven’t disclosed their preferences. So be careful while optimizing site considering different search engines.