function button_on(id)
    {
    document.getElementById(id).style.backgroundColor ='#ECECEC';
     }

function button_off(id)
    {
        document.getElementById(id).style.backgroundColor ='';
    }
    
 function gal_on(id)
    {
    document.getElementById(id).style.backgroundColor ='#F89838';
     }

function gal_off(id)
    {
        document.getElementById(id).style.backgroundColor ='#FFFFFF';
    }   
 
 function intro_on(id)
    {
    document.getElementById(id).style.backgroundColor ='#F1FAE2';
     }

function intro_off(id)
    {
        document.getElementById(id).style.background ='';
    } 
    
function toggle_help(element_name)   // pro ukázání náponědy
{
	var element = document.getElementById(element_name);
	if(element.style.display != "block"){
		element.style.display = "block";
	} else {
		element.style.display = "none";
	}
}