<div id="bax1" class="bax">
  <span class="bax3" onclick="closeSearch()" title="Close bax">x</span>
  <div class="bax-content">
    <form action="#">
      <input type="text" placeholder="Search for example.com" name="search">
      <button type="submit"><i class="fa fa-search"></i></button>
    </form>
  </div>
</div>
<button class="bax2" onclick="openSearch()">Click Open Search</button>

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
body {
  font-family: tahoma;
}

* {
  box-sizing: border-box;
}

.bax2 {
  background: #007FFF;
  border: 1px solid #ccc;
  padding: 10px 15px;
  font-size: 20px;
  cursor: pointer;
color:#fff;
}

.bax2:hover {
  background: #87ceeb;
color:#000;
}

.bax {
  height: 100%;
  width: 100%;
  display: none;
  position: fixed;
  z-index: 1;
  top: 0;
  left: 0;
  background-color: rgb(0,0,0);
  background-color: rgba(0,0,0, 0.9);
}

.bax-content {
  position: relative;
  top: 46%;
  width: 80%;
  text-align: center;
  margin-top: 30px;
  margin: auto;
}

.bax .bax3 {
  position: absolute;
  top: 20px;
  right: 45px;
  font-size: 60px;
  cursor: pointer;
color: yellow;
}

.bax .bax3:hover {
  color: #ccc;
}

.bax input[type=text] {
  padding: 15px;
  font-size: 17px;
  border: none;
  float: left;
  width: 80%;
  background: #007FFF;
color: #fff;
}

.bax input[type=text]:hover {
  background: #87ceeb;
color: #000;
}

.bax button {
  float: left;
  width: 20%;
  padding: 15px;
  background: cyan;
  font-size: 17px;
  border: none;
  cursor: pointer;
}

.bax button:hover {
  background: #fff;
}

function openSearch() {
  document.getElementById("bax1").style.display = "block";
}

function closeSearch() {
  document.getElementById("bax1").style.display = "none";
}

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