When would this be useful? If your site has a blog with public commenting turned on, links within those comments could pass your reputation to pages that you may not be comfortable vouching for. Blog comment areas on pages are highly susceptible to comment spam. Nofollowing these user-added links ensures that you're not giving your page's hard-earned reputation to a spammy site.
More than three billion people in the world are active on the Internet. Over the years, the Internet has continually gained more and more users, jumping from 738 million in 2000 all the way to 3.2 billion in 2015.[9] Roughly 81% of the current population in the United States has some type of social media profile that they engage with frequently.[10] Mobile phone usage is beneficial for social media marketing because of their web browsing capabilities which allow individuals immediate access to social networking sites. Mobile phones have altered the path-to-purchase process by allowing consumers to easily obtain pricing and product information in real time[11]. They have also allowed companies to constantly remind and update their followers. Many companies are now putting QR (Quick Response) codes along with products for individuals to access the company website or online services with their smart phones. Retailers use QR codes to facilitate consumer interaction with brands by linking the code to brand websites, promotions, product information, and any other mobile-enabled content. In addition, Real-time bidding use in the mobile advertising industry is high and rising due to its value for on-the-go web browsing. In 2012, Nexage, a provider of real time bidding in mobile advertising reported a 37% increase in revenue each month. Adfonic, another mobile advertisement publishing platform, reported an increase of 22 billion ad requests that same year.[12]
In addition to giving you insight into the search volume and competition level of keywords, most keyword research tools will also give you detailed information about the average or current estimated CPC for particular keywords are. This is particularly important for businesses with smaller ad budgets and this feature allows you to predict whether certain keywords will be truly beneficial to your ad campaigns or if they’ll cost too much.
Many blogging software packages automatically nofollow user comments, but those that don't can most likely be manually edited to do this. This advice also goes for other areas of your site that may involve user-generated content, such as guest books, forums, shout-boards, referrer listings, etc. If you're willing to vouch for links added by third parties (for example, if a commenter is trusted on your site), then there's no need to use nofollow on links; however, linking to sites that Google considers spammy can affect the reputation of your own site. The Webmaster Help Center has more tips on avoiding comment spam40, for example by using CAPTCHAs and turning on comment moderation.

By relying so much on factors such as keyword density which were exclusively within a webmaster's control, early search engines suffered from abuse and ranking manipulation. To provide better results to their users, search engines had to adapt to ensure their results pages showed the most relevant search results, rather than unrelated pages stuffed with numerous keywords by unscrupulous webmasters. This meant moving away from heavy reliance on term density to a more holistic process for scoring semantic signals.[13] Since the success and popularity of a search engine is determined by its ability to produce the most relevant results to any given search, poor quality or irrelevant search results could lead users to find other search sources. Search engines responded by developing more complex ranking algorithms, taking into account additional factors that were more difficult for webmasters to manipulate. In 2005, an annual conference, AIRWeb, Adversarial Information Retrieval on the Web was created to bring together practitioners and researchers concerned with search engine optimization and related topics.[14]
×