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.
In December 2009, Google announced it would be using the web search history of all its users in order to populate search results.[33] On June 8, 2010 a new web indexing system called Google Caffeine was announced. Designed to allow users to find news results, forum posts and other content much sooner after publishing than before, Google caffeine was a change to the way Google updated its index in order to make things show up quicker on Google than before. According to Carrie Grimes, the software engineer who announced Caffeine for Google, "Caffeine provides 50 percent fresher results for web searches than our last index..."[34] Google Instant, real-time-search, was introduced in late 2010 in an attempt to make search results more timely and relevant. Historically site administrators have spent months or even years optimizing a website to increase search rankings. With the growth in popularity of social media sites and blogs the leading engines made changes to their algorithms to allow fresh content to rank quickly within the search results.[35] 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
Provide full functionality on all devices. Mobile users expect the same functionality - such as commenting and check-out - and content on mobile as well as on all other devices that your website supports. In addition to textual content, make sure that all important images and videos are embedded and accessible on mobile devices. For search engines, provide all structured data and other metadata - such as titles, descriptions, link-elements, and other meta-tags - on all versions of the pages.

Another reason is that if you're using an image as a link, the alt text for that image will be treated similarly to the anchor text of a text link. However, we don't recommend using too many images for links in your site's navigation when text links could serve the same purpose. Lastly, optimizing your image filenames and alt text makes it easier for image search projects like Google Image Search to better understand your images.
WhatsApp was founded by Jan Koum and Brian Acton.WhatsApp joined Facebook in 2014, but continues to operate as a separate app with a laser focus on building a messaging service that works fast and reliably anywhere in the world.WhatsApp started as an alternative to SMS. Whatsapp now supports sending and receiving a variety of media including text, photos, videos, documents, and location, as well as voice calls. Whatsapp messages and calls are secured with end-to-end encryption, meaning that no third party including WhatsApp can read or listen to them. Whatsapp has a customer base of 1 billion people in over 180 countries.[46][47] It is used to send personalised promotional messages to individual customers. It has plenty of advantages over SMS that includes ability to track how Message Broadcast Performs using blue tick option in Whatsapp. It allows sending messages to Do Not Disturb(DND) customers. Whatsapp is also used to send a series of bulk messages to their targeted customers using broadcast option. Companies started using this to a large extent because it is a cost effective promotional option and quick to spread a message. Still, Whatsapp doesn't allow businesses to place ads in their app.[48]
All sites have a home or "root" page, which is usually the most frequented page on the site and the starting place of navigation for many visitors. Unless your site has only a handful of pages, you should think about how visitors will go from a general page (your root page) to a page containing more specific content. Do you have enough pages around a specific topic area that it would make sense to create a page describing these related pages (for example, root page -> related topic listing -> specific topic)? Do you have hundreds of different products that need to be classified under multiple category and subcategory pages?
In 1998, two graduate students at Stanford University, Larry Page and Sergey Brin, developed "Backrub", a search engine that relied on a mathematical algorithm to rate the prominence of web pages. The number calculated by the algorithm, PageRank, is a function of the quantity and strength of inbound links.[22] PageRank estimates the likelihood that a given page will be reached by a web user who randomly surfs the web, and follows links from one page to another. In effect, this means that some links are stronger than others, as a higher PageRank page is more likely to be reached by the random web surfer.