* {
    padding: 0;
}
html {
    background-image: url("citron.jpg");
    background-repeat: repeat-y;
    background-size: cover;
}

body {
    background-color:rgba(0, 0, 0, 0.5);
    border-radius: 10px;
    padding: 20px;
    padding-top: 1px;
}

table {
    border-collapse: collapse;
    border-spacing: 0;
    width: 100%;
    border: 3px solid #ddd;
    border-left: 0;
    border-right: 0;
}
ul {
    margin-left: 20px;
}
th, td {
    text-align: left;
    padding: 8px;
}
.helper {
    display: none;
}  

@media (max-width : 600px) {
    body {
        text-align: center;
    }
    .helper {
        display: block;
        color: red;
    }
}