<h1>I'm a default h1 element</h1>
<h1>I'm a default h1 element</h1>
<h1 id="addMargin">I'm an h1 element with margin-top: 100px</h1>
<h1>I'm another default h1 element</h1>

 #addMargin {
    margin-top: 100px;
}

body {
  margin: 0px;
}