function switchImage(newImageId, imageSource)
{
    var image = document.getElementById(newImageId);
   if ( image != null ) image.src =  imageSource;
}

function calcHeight(diff) {
	
  var  myHeight = 0;
  if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) 
  {
    myHeight = document.documentElement.clientHeight;
   document.getElementById('middle').height=myHeight-diff; 
  }
}