* { box-sizing: border-box; }
#contactForm { 
  display: none;
  border: 0.1em solid black; 
  padding: 0.3em;
  text-align: center;
  background: #ffd500;
  position: fixed;
  top:40%;
  left:50%;
  transform: translate(-50%,-50%);
  -webkit-transform: translate(-50%,-50%)
}