1.css

.js-warn {
  background: #EEE;
  color: #555;
  display: block;
  width: 30%;
  right: 0;
  left: 0;
  margin-right: auto;
  margin-left: auto;
  margin-top: 50px;
  border-radius: 10px;
  box-shadow: 0 10px 70px;
  text-align: center;
  position: fixed;
  font-family: sans-serif, serif;
  font-weight: 300;
  z-index: 9999;
}
.js-warn h1 {
  font-family: sans-serif, serif;
  font-weight: 300;
  padding: 10px 10px 0 10px;
}
.js-warn p {
  font-family: sans-serif, serif;
  padding: 0 10px 10px 10px;
}
.js-warn a {
  color: #355980;
  text-decoration: none;
  transition: all 0.2s linear;
}
.js-warn a:hover {
  color: #000;
}
#js-hide:checked ~ #js-warn-exit {
  display: none;
}
#js-hide {
  position: fixed;
  left: 100%;
}
#js-warn-exit {
  padding: 1em;
  overflow: auto;
}
#js-warn-exit label {
  background: #355980;
  color: white;
  padding: 0.5em 0.75em;
  cursor: pointer;
  border-radius: 3px;
  float: right;
}

@media screen and (max-width: 700px) {
  .js-warn {
    width: 60%;
  }
}

@media screen and (max-width: 400px) {
  .js-warn {
    width: 80%;
  }
  .js-warn h1 {
      font-size: large;
      font-weight: 500;
  }
}