   @media only screen and (mix-device-width : 480px){
}
   @media only screen and (max-device-width : 480px){
}
.alerta{
display:block;

}              
.span_vencimiento_ventas  {
color:white;}

#body_de_ventas {

    background:url(imagenes/fondocomerpagaventas.png?a=29) !important;
    background