Do-it-Yourself Marketing/ Pt. 10 HOW SEARCH ENGINES WORK[pt i ]

How do Search Engines Work ?

A Preview 

Software programs called spiders/crawlers visit all the web pages on the internet, 

to read/interpret their stored data. The pages that show up with the engines 

search results are termed  search engine results pages(SERP).The SERP is divided  
into sections,  see fig. 2-1 below.

1. Vertical Navigation, includes images,news, videos,maps etc.
2. Search Query Box shows your query
3. Results information provides a little meta info about your query results
4. Paid search advertising
5. Natural results
6. Query refinement suggestions

Crawling and Indexing
Picture the World Wide Web is a a series of stops on the subway. Each stop is

a unique document of some sort (usually a web page). Spiders need to crawl 

the entire subway line,so they use the best path available, which is the "links" 

between the web pages. This link structure binds together, all the pages that 

were made public, by someone who had linked to them.

Where do crawls begin ? At the most trusted websites.
The click distance of your website from the most trusted, is an indication of how 

trustworthy your site is.

Rankings
After retrieving the results most suited to any particular query, engines  rank 

them in order of importance/popularity, after taking the trust & authority factors 

into account, by using algorithms.

Relevance of a document increases if the search terms occur several times, 

showing up in the title,headlines,subheads, or links from other relevant pages, 

that use relevant anchor text.
Importance is gained by the number of references from other documents.

Evaluating Wed Page Content
Engines place high value on content. They analyze all of the words on the page 

& builds a semantic map, that it uses to match web pages to queries.
Because navigational elements are not generally unique to each page, they are 

not considered by engines, as they look for the unique content of each page.

What Content is Seen By Search Engines?
The spiders see the HTML code for your website, & ignore anything not related to 

the "real" content.

The page title is one of the most important factors determining ranking, however 

it is not always used, as with Yahoo or DMOZ directory listings, that may choose to

use the title that was used in your listings in these 2 directories. This problem can 

be solved using meta tags such as NOODP tag or DOYDIR tag.

 Meta keywords are ignored by Google, because of spammers, however Bing & 

Yahoo do seem to reference it in some way.

The meta description tag does not influence ranking, rather the engines use it as 

the description in the SERP, thusly your description should be well written.

The 4th element seen is the "ALT" attribute for images.
It tells engines what the image is about, which gives more info about the page 

content. ALT serves vision impaired people.

An image tag example:(img src+"http://www.websitename.com/img/nameofimage.jpg" alt="description of picture"border="0"/)
The src tells where the image is located. The section starting with ALT is the alt 

attribute. The attribute is what the engines read.