body {
    background-color: #4cff00;
}

.zahlavi {
    width: 100%;
    background-color:Highlight;
    height: 50px;
    text-align: center;
    font-size: 40px;
    margin-left: auto;
    margin-right: auto;
}

.clanek {
    box-sizing: border-box;
    width: 100%;
    height: 600px;
    margin: 20px 0;
    padding: 15px;
    background-color: Highlight;
}

@media screen and (min-width: 900px) {
    .clanek {
        width: 79%;
        float: left;
    }
}

.postrannipanel {
    box-sizing: border-box;
    width: 100%;
    height: 400px;
    margin: 20px 0;
    padding: 10px;
    background-color: Highlight;
}

@media screen and (min-width: 900px) {
    .postrannipanel {
        width: 20%;
        float: right;
        height: 240px;
        top: 40px;
        position: relative;
    }
}

.panel1 {
    text-align: center;
    background-color: #808080;
}

.panel2 {
    text-align: center;
    background-color: Highlight;
}