* {
  box-sizing: border-box;
}


.header {
  background-color: #f1f1f1;
  padding: 20px;
  text-align: center;
}

.topnav {
  overflow: hidden;
  background-color: #333;
}

/* Style the topnav links */
.topnav a {
  float: left;
  display: block;
  color: #f2f2f2;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

/* Change color on hover */
.topnav a:hover {
  background-color: #ddd;
  color: black;
}

.column {
  float: left;
  padding: 10px;
}

/* Main column */
.column.main {
  width: 75%;
}

/* right column */
.column.side {
  width: 25%;
}

/* Clear floats after the columns */
.row:after {
  content: "";
  display: table;
  clear: both;
}
  
.footer {
  padding: 20px;
  text-align: center;
  background: #ddd;
  margin-top: 20px;
}