body, #frmPrincipal {
    height: 100% !Important;
}

@media (max-height: 502.98px) {
   #divPrincipal {
        padding-top: 0;                
    }
}

@media (min-height: 503px) and (max-height: 699.98px) {
    #divPrincipal {
        padding-top: 0;
        margin: 0;
        
        position: fixed;
        top: 50%;
        left: 50%;
        
        transform: translate(-50%, -50%);
        
        outline: 1px solid transparent;
    }
}