$(document).ready( function () { 
 
    // On cache les sous-menus : 
	$("#navigation li ul").hide();  
    
	$("#navigation li").hover(function(){
		var $this = $(this);
		var $sub = $this.children('ul');

		if ($sub.length === 0) {return;}
			//$sub.slideDown('fast');
			$sub.show();
    }, function(){
    	var $this = $(this);
    	var $sub = $this.children('ul');
    	//$sub.slideUp('fast');
    	$sub.hide();
    });
        
} ) ;