div{
    width: 320px;
    height: 160px;
    border: 1px solid #333;
    margin: 10px auto;
    background-color : RGBa(255, 255, 0, 0.2);
}

#ex1, #ex2, #ex3{
    background-image: 
	url("../images/smilesmall.jpg");
}
#ex1{
    background-size: contain;
    background-repeat: no-repeat;
}
#ex2{
    background-size: cover;
    background-repeat: no-repeat;
}
#ex3{
    background-size: 25% 50%; 
	/*25% de la largeur du fond, 
	*50% de sa hauteur*/
    background-repeat: repeat;
}
#ex4{
    background-image: 
	url("../images/smilesmall.jpg"), 
	url("../images/thinksmall.jpg");
    background-size: 25% 50%, contain;
    background-repeat: repeat-x, repeat;
}