 <style>
        * {
        box-sizing: border-box;
        }

    .menu {
        float:left;
        width:20%;
        text-align:left;
        }

    .menu a {
        background-color:rgb(241, 251, 255);
        padding:8px;
        margin-top:7px;
        display:block;
        width:100%;
        color:222222;
        }
    
    .main {
        background-color:white;
        float:left;
        width:60%; padding:0 20px;
        }

    @media only screen and (max-width:620px) 
        {
        /* For mobile phones: */
        .menu, .main 
        {
        width:100%;
        }
        }
    </style>