<div id="netsidebar" class="netbar">
  <a href="javascript:void(0)" class="closenet" onclick="closeNav()">x</a>
  <a href="#">Page#1</a>
  <a href="#">Page#2</a>
  <a href="#">Page#3</a>
  <a href="#">Page#4</a>
</div>

<button class="opennet" onclick="openNav()">Sidebar panel <font color="red">☰</font></button> 

.netbar  {
  width: 0;
  position: fixed;
  z-index: 1;
  height: 250px;
  top: 0;
  left: 0;
  background-color: #0d0d0d;
  overflow-x: hidden;
  transition: 0.5s;
  padding-top: 60px;
border-radius: 0px;
border-top: 4px solid #960018;
border-bottom: 4px solid #960018;
}

.netbar a {
  padding: 8px 8px 8px 32px;
  text-decoration: none;
  font-size: 25px;
  color: #ccc;
  display: block;
  transition: 0.3s;
border: 1px solid #222;

}

.netbar a:hover {
  color: #555;

}

.netbar .closenet {
  position: absolute;
  top: 0;
  right: 25px;
  font-size: 36px;
color: red;
border: 0px solid #222;
}

.opennet{
  font-size: 20px;
  cursor: pointer;
  background-color: #18191b;
  color: #fff;
  padding: 10px 15px;
  border: none;
border-radius: 4px;
}


.opennet:hover {
  background-color:gray;
 color: #000;
}

function openNav() {
  document.getElementById("netsidebar").style.width = "250px";
}

function closeNav() {
  document.getElementById("netsidebar").style.width = "0";
}

<iframe src="https://www.netbax.net/tab/creation/sidebar-panel.html" style="width: 550px; height:550px;" frameborder="0"></iframe>