.muestra{
    height: 300px;
    width: 400px;
    border: 5px solid #C00;
    margin: 20px;
    padding: 20px;

    background: 
    url(f01.png) left bottom repeat-x,
    url(f02.png) left bottom no-repeat,
    url(f03.png) left top repeat-x;
    background-color: #a4d3ff;
}
    

.anterior , .posterior{
    height: 126px;
    width: 200px;
    border: 2px solid #30f;
    padding: 5px;

    background: 
    url(f01.png) left bottom repeat-x ,
    url(f02.png) left bottom no-repeat,
    url(f03.png) left top repeat-x;
    background-color: #a4d3ff;
}