how to set style rules for visited and unvisited links in a nav bar

  
    /* 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;
}