The majority of web traffic is driven by the major commercial search engines, Google, Bing, and Yahoo!. Although social media and other types of traffic can generate visits to your website, search engines are the primary method of navigation for most Internet users. This is true whether your site provides content, services, products, information, or just about anything else.
When the ad spot is part of a search engine results page (SERP), the automated auction takes place whenever a search for the keyword that is being bid upon occurs. All bids for the keyword that target the searcher's Geo-location, the day and time of the search, etc. are then compared and the winner determined. In situations where there are multiple ad spots, a common occurrence on SERPs, there can be multiple winners whose positions on the page are influenced by the amount each has bid. The bid and Quality Score are used to give each advertiser's advert an ad rank. The ad with the highest ad rank shows up first. The predominant three match types for both Google and Bing are broad, exact and phrase match. Google also offers the broad modifier match type which differs from broad match in that the keyword must contain the actual keyword terms in any order and doesn't include relevant variations of the terms.[6]

Along with the positive terms, negative keywords can be added to help remove unqualified traffic. For example, someone who searches for “free coffee table” isn’t looking to buy. By adding “free” as a negative keyword, the advertiser’s ad will not show when a query containing this term is typed. For a company selling high end products, “bargain” or “cheap” related terms may make good negative keywords.

Nathan: The comment by Mansi Rana helps answer your question. The fact is, the PageRank scores that were visible in the Google Toolbar hadn’t been updated in a long time (2+ YEARS), so they were probably getting more and more out-of-date anyway. The main reason Google would make them disappear, though, is that Google wants website owners to focus on the user and on quality content, not on trying to game the system with links.

Google's founders, in their original paper,[17] reported that the PageRank algorithm for a network consisting of 322 million links (in-edges and out-edges) converges to within a tolerable limit in 52 iterations. The convergence in a network of half the above size took approximately 45 iterations. Through this data, they concluded the algorithm can be scaled very well and that the scaling factor for extremely large networks would be roughly linear in {\displaystyle \log n} , where n is the size of the network.
Search engine optimization (SEO) is often about making small modifications to parts of your website. When viewed individually, these changes might seem like incremental improvements, but when combined with other optimizations, they could have a noticeable impact on your site's user experience and performance in organic search results. You're likely already familiar with many of the topics in this guide, because they're essential ingredients for any web page, but you may not be making the most out of them.

Digital marketing methods such as search engine optimization (SEO), search engine marketing (SEM), content marketing, influencer marketing, content automation, campaign marketing, data-driven marketing,[6] e-commerce marketing, social media marketing, social media optimization, e-mail direct marketing, display advertising, e–books, and optical disks and games are becoming more common in our advancing technology. In fact, digital marketing now extends to non-Internet channels that provide digital media, such as mobile phones (SMS and MMS), callback, and on-hold mobile ring tones.[7] In essence, this extension to non-Internet channels helps to differentiate digital marketing from online marketing, another catch-all term for the marketing methods mentioned above, which strictly occur online.

You want better PageRank? Then you want links, and so the link-selling economy emerged. Networks developed so that people could buy links and improve their PageRank scores, in turn potentially improving their ability to rank on Google for different terms. Google had positioned links as votes cast by the “democratic nature of the web.” Link networks were the Super PACs of this election, where money could influence those votes.
Unlike most offline marketing efforts, digital marketing allows marketers to see accurate results in real time. If you've ever put an advert in a newspaper, you'll know how difficult it is to estimate how many people actually flipped to that page and paid attention to your ad. There's no surefire way to know if that ad was responsible for any sales at all.

For example, suppose you're a law firm targeting the phrase "divorce attorney" with a broad match ad. Your ad should appear on the results page for the search query "divorce attorney," but it could also show up for the phrases "reasons for divorce," "dui attorney" or "dealing with divorce for children." In these cases, you may be wasting money on irrelevant searches.

Paid search functions as an auction. Advertisers bid on keywords that are relevant to their business that can trigger the display of their ads when users search for those terms. A wide range of factors determine where an ad will be shown on the SERP. Some ads might be displayed above the organic search results (such as the Lowe’s, Craftsman, and Husqvarna examples in the “lawnmowers” SERP example above), whereas others may be shown to the right of the organic results. Some advertisers choose to limit the display of their ads to mobile searches only, whereas others exclude mobile results altogether. Some ads feature extensions, and some do not.
Numerous academic papers concerning PageRank have been published since Page and Brin's original paper.[5] In practice, the PageRank concept may be vulnerable to manipulation. Research has been conducted into identifying falsely influenced PageRank rankings. The goal is to find an effective means of ignoring links from documents with falsely influenced PageRank.[6]
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."