var current_sub = '';
function showsub(subitem){
	if(current_sub !== subitem){
		
		if(document.getElementById(current_sub + '_button') != null){
			var image = document.getElementById(current_sub + '_button').src
			document.getElementById(current_sub + '_button').src = image.replace('_on','_off');
		}
		
		if(document.getElementById(subitem + '_button') != null){
			var image = document.getElementById(subitem + '_button').src
			document.getElementById(subitem + '_button').src = image.replace('_off','_on');
		}
	}
	if(current_sub !== subitem && subitem !== 'home'){
		if(document.getElementById(current_sub + '_sub') != null){
			document.getElementById(current_sub + '_sub').style.display = 'none';
		}
			current_sub = subitem;
			document.getElementById(subitem + '_sub').style.display = 'block';
	} else if(subitem == 'home'){
		if(document.getElementById(current_sub + '_sub') != null){
			document.getElementById(current_sub + '_sub').style.display = 'none';
		}
		current_sub = subitem;
	}
}