Search Engine works as answering machine. When a person perform an online search, search engine does two things: firstly, it returns only those results that are useful and relevant to searcher’s query and second, it ranks those results according to the popularity of the websites serving the information. The information given by search engine may be images, mix of web pages and other type of data and files. search engine follow some important seo rule for page ranking of large no of web sites.

Search engine basically operates three steps:

(1).Crawling

(2).Indexing

(3).Searching

(1) Crawling:

A web crawler started with the list of URLs for visit. When the crawler visit these URLs, it identifies all the hyperlinks in the page and add them to the list of URLs for visit, it is known as crawl frontier.

(2) Indexing:

is basically taking thing in a word order. Suppose a document on web contain name A B, and in the document A B appears next to each other. whenever a visitor search such document, Google indexing will search web-pages that contain words A and B. indexing will find most relevant documents or files that contain word A B on the page or may be back links in anchor text pointing to that document. The main purpose of indexing is to optimize performance and speed in finding relevant documents for search query.

(3) Searching:

Once the document selection done, next is, how to rank those documents. We use PR and two hundred other factors for ranking. Like document A B, may be this document is popular, or very authoritative, or it having more back-links on web having lot of repetition. So Google try to balance all two hundred ranking signals to find most relevant document or best match for the query. And then it display all the related information, keywords, contact details and link associated with that query.