// return the height of the content window
 function getWindowHeight() {
  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;
  }
   
   return myHeight;
}
 
 /*
	center page vertically 
	divGeral it's the main content div
 */
 function centerVertically () {
	var divGeral 		= document.getElementById("geral");
	var windowHeight	= getWindowHeight() ;
	var divGeralHeight 	= divGeral.offsetHeight;
 
	 // it's only needed to center page if div height is lower then window height
	if (divGeralHeight < windowHeight) {
		divGeral.style.marginTop 	= ((windowHeight - divGeralHeight) / 2) + "px";
	}
	
 
 }