#cabecera{
    width: 99.5%;
    height: 80px;
    background-color: royalblue;
}
#columna_izquierda{
    float: left;
    width: 30%;
    height: 480px;
    background-color: sandybrown;
}
#columna_derecha{
    float:left;
    width: 69.5%;
    height: 480px;
    background-color: lightgreen;
}
#pie{
    clear:both;
    width: 99.5%;
    height: 80px;
    background-color: violet;
}