//Swap l'image de fond de la navigation RollOver
function swapNavig(target, background) {

	if(background != ''){
		
		document.getElementById(target).style.backgroundImage = 'url('+background+')'; 
		document.getElementById(target).style.backgroundPosition = 'bottom'; 
		document.getElementById(target).style.backgroundRepeat = 'repeat-x';
	}
	else document.getElementById(target).style.backgroundImage = 'none'; 
}