#alerta{display: block;}

@media only screen and (min-width: 1536px){
    #alerta{width: 1230px; top: -50px; font-size: 1.65em; margin: 25px auto; }
}

@media only screen and (max-width: 1535px) and (min-width: 1024px){
    #alerta{width: 1000px;  top: -50px; font-size: 1.65em; margin: 25px auto; }
}

@media only screen and (max-width: 1023px) and (min-width: 768px){
    #alerta{width: 700px;  top: -50px; font-size: 1.65em; margin: 15px auto; }
}

@media only screen and (max-width: 767px) {
    #alerta{width: 350px; top: -50px; font-size: 1.45em; margin: 10px auto; }
}