Coming and going of websites & link:
"The estimated minimal size of the indexed World Wide Web is based on the estimations of the numbers of pages indexed by Google, Bing, Yahoo Search. From the sum of these estimations, an estimated overlap between these search engines is subtracted...The size of the index of a search engine is estimated on the basis of a method that combines word frequencies obtained in a large offline text collection (corpus), and search counts returned by the engines. Each day 50 words are sent to all four search engines. The number of webpages found for these words are recorded; with their relative frequencies in the background corpus, multiple extrapolated estimations are made of the size of the engine's index, which are subsequently averaged. The 50 words have been selected evenly across logarithmic frequency intervals (see Zipf's Law)." Source
"The life span of a Google query is less then 1/2 second, and involves quite a few steps before you see the most relevant results. Here's how it all works." | http://www.google.com/howgoogleworks |
Explanation from SearchEngineLand.com:
'SEO stands for “search engine optimization.” It is the process of getting traffic from the “free,” “organic,” “editorial” or “natural” listings on search engines.'
"The latest stories about Search Engine Optimization (SEO) and search engine updates that affect website ranking on search engines."
This information is outdated, but the categories and company trends are still valuable.