CODE EXAMPLE FOR CSS

html media query

<style>
  .example1 {margin:10px auto; background:deepskyblue}
@media (max-width:600px)
{
  .example1 {width:70px; height:50px}
}
@media (min-width:600px)
{
  .example1 {width:100px; height:50px}
}
</style>
<div id="example1">Hi</div>