function hideX(n)
{
	var x = document.getElementById('bloc'+n) ;
	var y = document.getElementById('img'+n) ;
	
	if (x.style.display == "block") 
	{
		x.style.display = "none";
		y.src = "/multimedia/images/img_structures/expand_.gif" ;
	} 
	else 
	{
		x.style.display = "block";
		y.src = "/multimedia/images/img_structures/collapse_.gif" ;
	}
}