About Search Engine
What is a Search Engine?
Search Engine Definition: An internet-based tool that searches an index of documents for a particular term ( keyword ), phrase or text specified by the user. Commonly refer to search engines that search through billions of pages on the internet.
Search Engine Characteristics:
• Spider, Indexer, Database, Algorithm
• According to relevance finding matching documents and display them
• Frequent updating to searched documents and ranking algorithm
• Produces “better”, more relevant results than competitors
Major Search Engines
• Google feeds AOL, Netscape, Earthlink & others
• Yahoo owns Overture, AltaVista, AlltheWeb, FAST & others
• Google, Yahoo & MSN results account for 80-90% of all search traffic.
Goals & Objectives
• To search it accumulate large index (database) of web documents.
• Provide highly-relevant results to users.
• Generate revenue by generating large amount of traffic via paid advertising.
How Do Search Engines Work?
• Spider “crawls” the web by following hyperlinks from websites already in the database to find new documents (web pages).
• Search engine indexes the content (text / code) by adding it to their huge databases and updating it periodically.
• When user enters to find related documents. In real-time search engine searches its own database but does not search web pages.
• Resulting documents are ranked by Search engine using an algorithm (mathematical formula) according to various ranking factors various weights are assigned.
Ranking Factors
On-Page Factors (Code & Content)
• Title tags
• Header tags
. ALT image tags
• Content, Content, Content (Body text)
• Hyperlink text
• Keyword frequency & density
Off-Page Factors
• Link Popularity
• Anchor text
What is the Algorithm?
• Algorithm is Mathematical formula Reverse engineering, research and experiments gives SEO (search engine optimization professionals) a “pretty good” idea of major factors and approximate weight assignments.
• Constantly changing, tweaking, updating is done to the algorithm
• Websites and documents being searched are also constantly changed by algorithm.
• Algorithm Varies by Search Engine – some give more weight to on-page factors , some to link popularity
