Once search engines like google and yahoo have crawled pages at the web, they are able to extract the content material of these pages and upload it to their indexes. In this manner, they are able to decide in the event that they experience a web page is of enough excellent to be ranked nicely for relevant keywords (Google created a short video to explain that technique). When they're deciding this, the engines like google do no longer just study the content material of the web page; they also examine the wide variety of hyperlinks pointing to that page from external web sites and the first-class of these external websites.
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