an entirely revamped edition of twitter.com. Changes included the ability to see pictures and videos without leaving Twitter itself by clicking on individual tweets which contain links to images and clips from a variety of supported websites, including YouTube and Flickr, and a complete overhaul of the interface, which shifted links such as '@mentions' and 'Retweets' above the Twitter stream, while 'Messages' and 'Log Out' became accessible via a black bar at the very top of twitter.com. As of November 1, 2010, the company confirmed that the "New Twitter experience" had been rolled out to all users. In 2019, Twitter was announced to be the 10th most downloaded mobile app of the decade, from 2010 to 2019. On April 5, 2011, Twitter tested a new homepage and phased out the "Old Twitter". However, a glitch came about after the page was launched, so the previous "retro" homepage was still in use until the issues were resolved; the new homepage was reintroduced on April 20. On December 8, 2011, Twitter overhauled its website once more to feature the "Fly" design, which the service says is easier for new users to follow and promotes advertising. In addition to the Home tab, the Connect and Discover tabs were introduced along with a redesigned profile and timeline of Tweets. The site's layout has been compared to that of Facebook. On February 21, 2012, it was announced that Twitter and Yandex agreed to a partnership. Yandex, a Russian search engine, finds value within the partnership due to Twitter's real time news feeds. Twitter's director of business development explained that it is important to have Twitter content where Twitter users go. On March 21, 2012, Twitter celebrated its sixth birthday by announcing that it had 140 million users, a 40% rise from September 2011, who were sending 340 million tweets per day. On June 5, 2012, a modified logo was unveiled through the company blog, removing the text to showcase the slightly redesigned bird as the sole symbol of Twitter. On December 18, 2012, Twitter announced it had surpassed 200 million monthly active users. On January 28, 2013, Twitter acquired Crashlytics in order to build out its mobile developer products. On April 18, 2013, Twitter launched a music app called Twitter Music for the iPhone. On August 28, 2013, Twitter acquired Trendrr, followed by the acquisition of MoPub on September 9, 2013. As of September 2013,