Google Web Spider, Yahoo Web Spider
These spiders pay special attention to the non visible portion of the Web page which are the meta tags.
This brings us to our next point: What are meta tags?
Meta tags are keywords and concepts specified by the owner of a page under which the web page 
will be indexed. When the words on the web page might have double or triple meanings, meta tags can be extremely helpful by guiding the search engine to choose the correct meaning out of the several possibilities. However, over reliance on meta tags is risky since either a sly or a careless page owner might add meta tags for popular topic that have no relationship whatsoever to the actual content displayed on the web page. Spiders prevent this by checking to see if the page content correlates with the meta tags and rejecting meta tags that show discrepancy with the words on the page.
If you want your web page or website to come up with the search results on the search engine, you have to make sure that the web spider crawls your website. To accomplish that, there has to be a link to your website from another website. The main point of search engine optimization is the exchange of links.
Chicago SEO GROUP
On the web today, there are lots and lots of websites. Some are linked to others and some stand alone. Your website achieves a link when you link another website or when another website links you, or when you link both ways. This linkage, termed hyperlink, is a very essential component of the Internet and search engine optimization since it attracts the spider to your website with the ultimate result of providing a higher ranking. Websites that do not have any links and that nobody links to stand alone and are virtually ignored by the web spider; to put it simply, they are unreachable. Therefore Websites that stand alone never appear in search rankings. This is obviously not the optimal results for most people and companies that want to get their website seen; they want people to find their website and find it repeatedly. That’s why people spend thousands of dollars on search engine optimization.
