function affichage_pub()
{
	var cache = document.getElementById('cache').style;
	var pub = document.getElementById('pub').style;
	var img_pub = document.getElementById('img_pub');
	
	cache.width=document.body.clientWidth+'px';
	cache.height=document.body.clientWidth+'px';
	
	cache.display='block';
	pub.display='block';
	
	new Effect.Opacity('cache', { from: 0, to: 0.5, duration: 0.2 });
	pub.width=img_pub.offsetWidth+'px';
	pub.left=((document.body.offsetWidth-parseInt(pub.width))/2)+'px';
}

function fermer_pub()
{
	Effect.Fade('pub', { duration: 0.2 });
	Effect.Fade('cache', { duration: 0.2 });
}