<p>SAN FRANCISCO (Reuters) - More than 100 million people will be glued to their TV screens on Sunday, when the Denver Broncos take on the Seattle Seahawks in America's premier sporting contest, the Super Bowl.</p><p>But two fierce rivals, Facebook Inc and Twitter Inc, will also be clashing head-to-head on a "second screen" that TV viewers will tune in for the big game.</p><p>The two social networks are jostling to be the venue of choice for fans to comment on big plays, the star-studded halftime show and of course the commercials - multimillion dollar productions by major brands that are often a draw in their own right.</p><p>The Super Bowl is the biggest stage for a broader battle that has intensified over the past year between the two behemoths of social media. By dominating online chatter during events such as the American football game, each company hopes to attract users and advertisers and capture a slice of the $70 billion spent annually on U.S. television advertising.</p><p><a href="http://www.reuters.com/article/2014/01/31/us-nfl-superbowl-social-idUSBREA0U0C720140131">Keep reading...</a></p><p>Read also:</p><p><a href="http://finance.yahoo.com/blogs/talking-numbers/suddenly--twitter-is-cheap-150510115.html">Suddenly, Twitter is cheap</a> (Yahoo Finance (blog))</p><p><a href="http://www.businessinsider.com/facebooks-strategy-to-beat-twitter-during-the-super-bowl-2014-1">Here&#039;s Facebook&#039;s Strategy To Lure You Away From Twitter During The Super ...</a> (Business Insider)</p><p><a href="http://www.abs-cbnnews.com/business/02/01/14/its-facebook-vs-twitter-second-screen-crown-super-bowl">It&#039;s Facebook vs Twitter for &#039;second screen&#039; crown in Super Bowl</a> (ABS CBN News)</p><p>Explore: <a href="http://news.google.com/news/more?ncl=dwVydKydBxBa_oMIzoDBaq7K02hSM&authuser=0&ned=us">97 additional articles.</a></p>