.conteneur{
    width: 400px;
    height: 200px;
    border: 1px solid #333;
    margin: 10px auto;
    background-color : RGBa(255, 255, 0, 0.2);
    overflow: scroll;
}
p{
    font-size: 50px;
    text-align:center;
    color: #000;
    text-shadow: 0px 0px 1px #fff;
    background-color: RGBa(255,255,255,0.5);
}

#ex1, #ex2, #ex3{
    background-image: 
	url("../images/thinksmall.jpg");
    background-size: 100px;
    background-repeat: repeat;
    width: 385px;
    height: 300px;
    overflow: scroll;
}
#ex1{
    background-attachment: fixed;
}
#ex2{
    background-attachment: scroll;
}
#ex3{
    background-attachment: local;
}