a:link{
    background-color:#00ff00;
    color:#ff0000;
  }
  a:visited{
    background-color:#000000;
    color:#ffffff;
  }
  a:hover{
    background-color:#ff00ff;
    color:#fffff;
  }
  a:active{
    background-color:#ff0000;
    color:#ffff00;
  }