* {
  box-sizing: border-box;
}

.menu {
  float: left;
  width: 25%;
  text-align: center;
}

.menu a {
  background-color: #e5e5e5;
  padding: 8px;
  margin-top: 7px;
  display: block;
  width: 100%;
  color: black;
  border-bottom:1px solid #7f7f7f;
  text-decoration:none;
}
.menu a:hover {
color:white;
background-color:black;
}
.menu a.high {
 color:white;
background-color:red;
}
.main {
  float: left;
  width: 75%;
  padding: 0 20px;
}

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