<div class="hidden-div">
<button onClick="toggleFunction()"> Click Me to see magic </button>
</div>
<div id="another-div">
Visible sometimes invisible div
</div>
</div>

div.hidden-div {
  width: 100%;
  margin: 50px auto;
  text-align: center;
}
#another-div{
  width: 300px;
  height: 100px;
  margin: 50px auto;
  text-align: center;
  font-size: 2em;
  padding-top: 20px;
  border-radius: 150px;
  background-color: blue;
}

function toggleFunction(){
  var toggle = document.getElementById("another-div");
  if (toggle.style.display === "none") {
    toggle.style.display ="block";
  } else {
    toggle.style.display ="none";
  } 
}