Monday, January 16, 2012

How do web search engines (crawler-based search engine) work?

Search engines are used to find information on the Web. Search the Web, images, video, news from Google, Yahoo, Bing seems very simple. People just type queries in search box, search engine returns search results. But search engines are complex software system. Search engines utilize tens or hundreds of thousands of computers to process billions of web pages and return results for thousands of searches per second. Search can't find what is not on search engine. How do search engines find a website? Here are basic steps of how search engines work.

    1. Search engine crawls a website
  • Search engine uses spider (or crawler) visit a web site, read the information on the web pages, follow hyperlinks from one pages to another pages that the site connects to.
    2. Search engine stores each word in a searchable index
  • Search engine indexes the content(text, code) of the webpage by adding it to their giant database and then periodically updates this content.
    3. Search engine matches the query terms with words in the index
  • Search engines search their own giant databases when a user enters in a search query to find related documents sort documents by relevance.
    4. Search engine displays results
  • Search engines rank the resulting documents using an algorithm by assigning various weights and ranking factors.

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What is SEO?

What is SEO?

SEO stands for search engine optimization. It is web development for internet marketing.
Optimizing a website include on-site and off-site SEO. On-site SEO tasks involve content editing, content structuring and technical coding suggestions. Off-site SEO includes promoting website tasks such as increasing the number of high quality backlinks or inbound links.

SEO is a holistic subject. Being a good SEOs ( an acronym for "search engine optimizers") should understand how search engine works, understand search engine algorithms and ranking strategies. Doing SEO can't just only focus on the mechanical aspects of SEO, analyszing web traffic, testing keywords, comparing competitor websites are all vital to the success of SEO.

For SEO purpose you must remember:
1. Crawler-based search engine spider or crawler doesn't recognize images when crawling a webpage. You must help the spiders understand each of images with alt text. Google webmaster guidelines "Try to use text instead of images to display important names, content, or links. The Google crawler doesn't recognize text eontained in images. If you must use images for textual content, consider using the 'ALT' attribute to include a few words of descriptive text."

2. Crawler-based search engine is not human being, sometimes it might not get the meaning of a page right. You must help seach engine by optimizing the page to get higher ranking.

3. Search engines periodically change algorithms for returning the best results to users. You need to monitor your website and keep optimizing your website constantly.

 How do search engines work?