function showSubNavigationWorks(){
		document.getElementById("subNavigationWorks").style.visibility = "visible";
		document.getElementById("subNavigationPortraits").style.visibility = "collapse";
	}
	
	function showSubNavigationPortraits(){
		document.getElementById("subNavigationPortraits").style.visibility = "visible";
		document.getElementById("subNavigationWorks").style.visibility = "collapse";
	}
	
	function hideSubNavi(){
		document.getElementById("subNavigationPortraits").style.visibility = "collapse";
		document.getElementById("subNavigationWorks").style.visibility = "collapse";
	}