span inline

/* The sidebar menu */
.sidenav {
  height: 100%; /* 
Full-height: remove this if you want "auto" height */
  width: 160px; 
  /* Set the width of the sidebar */
  position: fixed; /* 
  Fixed Sidebar (stay in place on scroll) 
*/
  z-index: 1; /* Stay on top */
  
top: 0; /* Stay at the top */
  left: 0;
  
background-color: #111; /* Black */
  
overflow-x: hidden; /* Disable horizontal scroll */
  
  padding-top: 20px;

}

/* The navigation menu links */
.sidenav a {
  padding: 
  6px 8px 6px 16px;
  
text-decoration: none;
  font-size: 25px;
  
color: #818181;
  display: block;
}

/* When you mouse over the navigation links, 
change their color */
.sidenav a:hover {
  
color: #f1f1f1;
}


/* Style page content */
.main {
  margin-left: 
  160px; /* Same as the width of the sidebar */
  padding: 
  0px 10px;
}

/* On smaller screens, where height is less than 
450px, change the style of the sidebar (less padding and a smaller font 
size) */
@media screen and (max-height: 450px) {
  .sidenav 
{padding-top: 15px;}
  .sidenav a {font-size: 18px;}

} 

  <!-- Side navigation -->
<div class="sidenav">
  <a href="#">About</a>
  
<a href="#">Services</a>
  <a href="#">Clients</a>
  <a href="#">Contact</a>

</div>

<!-- Page content -->
<div class="main">
  ...
</div>