File: style.css

html, body {
    margin : 0;
    padding : 0;
    font-size: 20px;    
}
.wrapper {
    width : 900px;
    margin : auto;
    text-align : center;
}
.header {
    background: #252592;
    overflow: hidden;
    color: white;
}

#click {
    display: inline-block;
    background: #74cc74;
    padding: 10px 20px;
}
.clank {
    background: #1790c7;
    padding: 5px;
    margin: 5px;
}
.row {
    padding: 20px 0;
}
.row2{
    background: rgba(173, 187, 193, 0.22);
    padding: 20px 0;
}
#box {
    width:200px;
    height:100px;
    background:#333;
    color:white;
    display : inline-block;
}
#single {
    background: red;
    display: inline-block;
    padding: 10px 20px;
    color: white;
}
.block {
    display: block;
    border: 1px solid black;
    padding: 10px 5px;
    margin: 20px;
    font-size: 18px;
    background : white;
    text-align : left;
}