$(document).ready(function() {
$('#lien1').css({backgroundPosition: '0px 0px'});
$('#lien2').css({backgroundPosition: '0px 0px'});
$('#lien3').css({backgroundPosition: '0px 0px'});
$('#lien4').css({backgroundPosition: '0px 0px'});
$(".link").hover(function(){
$(this).parent().animate({backgroundPosition: '(0px -21px)'}, 350 );
}, function() {
$(this).parent().animate({backgroundPosition: '(0px 0px)'}, 350 );
}); 
});