* {
    margin: 0px;
    padding: 0px;
}

body {
    background-color: #515151;
}

.imagencabecera {
    background: linear-gradient(90deg, rgba(20,129,0,1) 0%, rgba(255,255,255,1) 15%, rgba(0,0,0,1) 35%, rgba(0,0,0,1) 65%, rgba(255,255,255,1) 85%, rgba(20,129,0,1) 100%);
    width: 100%;
    height: 250px;
}

.imagencabecera img {
    width: 25%;
    height: 100%;
    margin-left: 37.5%;
}

@media (max-width: 960px) {
    .imagencabecera {
        height: 350px;
        background: linear-gradient(90deg, rgba(20,129,0,1) 0%, rgba(255,255,255,1) 10%, rgba(0,0,0,1) 25%, rgba(0,0,0,1) 75%, rgba(255,255,255,1) 90%, rgba(20,129,0,1) 100%);
    }

    .imagencabecera img {
        width: 40%;
        margin-left: 30%;
    }
}

@media (max-width: 700px) {
    .imagencabecera {
        background: linear-gradient(90deg, rgba(20,129,0,1) 0%, rgba(255,255,255,1) 5%, rgba(0,0,0,1) 15%, rgba(0,0,0,1) 85%, rgba(255,255,255,1) 95%, rgba(20,129,0,1) 100%);
    }

    .imagencabecera img {
        width: 70%;
        margin-left: 15%;
    }
}

@media (max-width: 420px) {
    .imagencabecera {
        background: black;
        height: 300px;
    }

    .imagencabecera img {
        width: 100%;
        margin-left: 0%;
    }
}