what should be in my style.css code example

Example 1: css how to style a

/*a normal, unvisited link*/
a:link{
	color: green;
}
/*a link the user has visited*/
a:visited{
	color: purple;
}
/*a link when the user mouses over it*/
a:hover{
	color: yellow;
}
/*a link the moment it is clicked*/
a:active{
	color: brown;
}

Example 2: css / style

<style>
  h2 {
    color: red;
  }
</style>
<!-- all h2 elements will become red for example -->
<h2>
  i am the best
  </h2>
<!-- i am the best would be red