function changeVisibility(element){
// on/off visibility of a div element in sequence

	if(document.getElementById(element).style.visibility == 'visible'){
																					 
	}
	else{
		  document.getElementById(element).style.visibility = 'visible';
		  document.getElementById(element).style.display = '';
	}

}

function correctVisibility(element){
	 document.getElementById(element).style.visibility = 'hidden';
	 document.getElementById(element).style.display = 'none';																			 
}