try this

add margin: 0px 0px to the body style and div.content style

add this code to the script GetUnity():

  var myWidth = 0, myHeight = 0;
  if( typeof( window.innerWidth ) == 'number' )
  {
    //Non-IE
    myWidth = window.innerWidth;
    myHeight = window.innerHeight;
  }
  else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) )
  {
    //IE 6+ in 'standards compliant mode'
    myWidth = document.documentElement.clientWidth;
    myHeight = document.documentElement.clientHeight;
  }
  else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) )
  {
    //IE 4 compatible
    myWidth = document.body.clientWidth;
    myHeight = document.body.clientHeight;
  }
  unityObject.embedUnity("unityPlayer", "MyAwesomGame.unity3d", myWidth , myHeight);

that may be more than you need but it works for me. When the page loads, it will set the game resolution to the current window size, so if they resize the window, it stays the same. If you want that to stretch to fit dynamically, that's something else.