Description meta tags are important because Google might use them as snippets for your pages. Note that we say "might" because Google may choose to use a relevant section of your page's visible text if it does a good job of matching up with a user's query. Adding description meta tags to each of your pages is always a good practice in case Google cannot find a good selection of text to use in the snippet. The Webmaster Central Blog has informative posts on improving snippets with better description meta tags18 and better snippets for your users19. We also have a handy Help Center article on how to create good titles and snippets20.
A navigational page is a simple page on your site that displays the structure of your website, and usually consists of a hierarchical listing of the pages on your site. Visitors may visit this page if they are having problems finding pages on your site. While search engines will also visit this page, getting good crawl coverage of the pages on your site, it's mainly aimed at human visitors.
When Googlebot crawls a page, it should see the page the same way an average user does15. For optimal rendering and indexing, always allow Googlebot access to the JavaScript, CSS, and image files used by your website. If your site's robots.txt file disallows crawling of these assets, it directly harms how well our algorithms render and index your content. This can result in suboptimal rankings.
With the development of this system, the price is growing under the high level of competition. Many advertisers prefer to expand their activities, including increasing search engines and adding more keywords. The more advertisers are willing to pay for clicks, the higher the ranking for advertising, which leads to higher traffic.[15] PPC comes at a cost. The higher position is likely to cost $5 for a given keyword, and $4.50 for a third location. A third advertiser earns 10% less than the top advertiser, while reducing traffic by 50%.[15] The investors must consider their return on investment and then determine whether the increase in traffic is worth the increase.
Robots.txt is not an appropriate or effective way of blocking sensitive or confidential material. It only instructs well-behaved crawlers that the pages are not for them, but it does not prevent your server from delivering those pages to a browser that requests them. One reason is that search engines could still reference the URLs you block (showing just the URL, no title or snippet) if there happen to be links to those URLs somewhere on the Internet (like referrer logs). Also, non-compliant or rogue search engines that don't acknowledge the Robots Exclusion Standard could disobey the instructions of your robots.txt. Finally, a curious user could examine the directories or subdirectories in your robots.txt file and guess the URL of the content that you don't want seen.

SEO may generate an adequate return on investment. However, search engines are not paid for organic search traffic, their algorithms change, and there are no guarantees of continued referrals. Due to this lack of guarantees and certainty, a business that relies heavily on search engine traffic can suffer major losses if the search engines stop sending visitors.[61] Search engines can change their algorithms, impacting a website's placement, possibly resulting in a serious loss of traffic. According to Google's CEO, Eric Schmidt, in 2010, Google made over 500 algorithm changes – almost 1.5 per day.[62] It is considered a wise business practice for website operators to liberate themselves from dependence on search engine traffic.[63] In addition to accessibility in terms of web crawlers (addressed above), user web accessibility has become increasingly important for SEO. Avatars United Bebo Bolt Capazoo eConozco Emojli Eyegroove FitFinder Formspring FriendFeed Friends Reunited Friendster Google+ Google Buzz Heello Hyves iTunes Ping iWiW Jaiku LunarStorm Me2day Meerkat Mobli Mugshot Natter Social Network Netlog Orkut Pheed Piczo PlanetAll Posterous Pownce Qaiku Surfbook tbh Tsū tvtag Vine Windows Live Spaces Wretch Yahoo! 360° Yahoo! Kickstart Yahoo! Mash Yahoo! Meme Yik Yak
While most search engine companies try to keep their processes a secret, their criteria for high spots on SERPs isn't a complete mystery. Search engines are successful only if they provide a user links to the best Web sites related to the user's search terms. If your site is the best skydiving resource on the Web, it benefits search engines to list the site high up on their SERPs. You just have to find a way to show search engines that your site belongs at the top of the heap. That's where search engine optimization (SEO) comes in -- it's a collection of techniques a webmaster can use to improve his or her site's SERP position.
Website owners recognized the value of a high ranking and visibility in search engine results,[6] creating an opportunity for both white hat and black hat SEO practitioners. According to industry analyst Danny Sullivan, the phrase "search engine optimization" probably came into use in 1997. Sullivan credits Bruce Clay as one of the first people to popularize the term.[7] On May 2, 2007,[8] Jason Gambert attempted to trademark the term SEO by convincing the Trademark Office in Arizona[9] that SEO is a "process" involving manipulation of keywords and not a "marketing service."