a:hover {
    background-color: yellow;
  }
  /* unvisited link */
a:link {
    color: green;
  }
  
  /* visited link */
  a:visited {
    color: green;
  }
  
  /* mouse over link */
  a:hover {
    color: red;
  }
  
  /* selected link */
  a:active {
    color: yellow;
  }