Efeito Neon em HTML e CSS

Crie um novo documento html e css (presumindo que você saiba linkar o css no html)

dentro do body do html coloque:

<div id="container">

  <p><a href="https://en.wikipedia.org/wiki/Red">
    RED
  </a></p>

  <p><a href="https://en.wikipedia.org/wiki/Blue">
    BLUE
  </a></p>

  <p><a href="https://en.wikipedia.org/wiki/Yellow">
    Yellow
  </a></p>

  <p><a href="https://en.wikipedia.org/wiki/Green">
    GREEN
  </a></p>

  <p><a href="https://en.wikipedia.org/wiki/Orange_(colour)">
    ORANGE
  </a></p>

  <p><a href="https://en.wikipedia.org/wiki/Violet_(color)">
    VIOLET
  </a></p>

</div>

<div id="linkBack" style="position:absolute;right:0px;top:0px;background-color:#333;margin:0;width:60px;padding:5px"><a href="http://www.f-rilling.com/projects/" target="_blank" style="font-size:14px;text-decoration:none;color:#fff;padding:0 0 0 5px;font-family:sans-serif">My Site</a></div>

Agora no CSS coloque:

body {
  background-color: #222222;
  background: repeating-linear-gradient(45deg, #2b2b2b 0%, #2b2b2b 10%, #222222 0%, #222222 50%) 0 / 15px 15px;
}

#container {
  width: 500px;
  margin: auto;
}

/*Neon*/
p {
  text-align: center;
  font-size: 7em;
  margin: 20px 0 20px 0;
}

a {
  text-decoration: none;
  -webkit-transition: all 0.5s;
  -moz-transition: all 0.5s;
  transition: all 0.5s;
}

p:nth-child(1) a {
  color: #fff;
  font-family: Monoton;
  -webkit-animation: neon1 1.5s ease-in-out infinite alternate;
  -moz-animation: neon1 1.5s ease-in-out infinite alternate;
  animation: neon1 1.5s ease-in-out infinite alternate;
}

p:nth-child(1) a:hover {
  color: #FF1177;
  -webkit-animation: none;
  -moz-animation: none;
  animation: none;
}

p:nth-child(2) a {
  font-size: 1.5em;
  color: #228DFF;
  font-family: Iceland;
}

p:nth-child(2) a:hover {
  -webkit-animation: neon2 1.5s ease-in-out infinite alternate;
  -moz-animation: neon2 1.5s ease-in-out infinite alternate;
  animation: neon2 1.5s ease-in-out infinite alternate;
}

p:nth-child(3) a {
  color: #FFDD1B;
  font-family: Pacifico;
}

p:nth-child(3) a:hover {
  -webkit-animation: neon3 1.5s ease-in-out infinite alternate;
  -moz-animation: neon3 1.5s ease-in-out infinite alternate;
  animation: neon3 1.5s ease-in-out infinite alternate;
}

p:nth-child(4) a {
  color: #B6FF00;
  font-family: "Press Start 2P";
  font-size: 0.8em;
}

p:nth-child(4) a:hover {
  -webkit-animation: neon4 1.5s ease-in-out infinite alternate;
  -moz-animation: neon4 1.5s ease-in-out infinite alternate;
  animation: neon4 1.5s ease-in-out infinite alternate;
}

p:nth-child(5) a {
  color: #FF9900;
  font-family: Audiowide;
}

p:nth-child(5) a:hover {
  -webkit-animation: neon5 1.5s ease-in-out infinite alternate;
  -moz-animation: neon5 1.5s ease-in-out infinite alternate;
  animation: neon5 1.5s ease-in-out infinite alternate;
}

p:nth-child(6) a {
  color: #BA01FF;
  font-family: Vampiro One;
}

p:nth-child(6) a:hover {
  -webkit-animation: neon6 1.5s ease-in-out infinite alternate;
  -moz-animation: neon6 1.5s ease-in-out infinite alternate;
  animation: neon6 1.5s ease-in-out infinite alternate;
}

p a:hover {
  color: #ffffff;
}
/*glow for webkit*/

@-webkit-keyframes neon1 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #FF1177, 0 0 70px #FF1177, 0 0 80px #FF1177, 0 0 100px #FF1177, 0 0 150px #FF1177;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #FF1177, 0 0 35px #FF1177, 0 0 40px #FF1177, 0 0 50px #FF1177, 0 0 75px #FF1177;
  }
}

@-webkit-keyframes neon2 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #228DFF, 0 0 70px #228DFF, 0 0 80px #228DFF, 0 0 100px #228DFF, 0 0 150px #228DFF;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #228DFF, 0 0 35px #228DFF, 0 0 40px #228DFF, 0 0 50px #228DFF, 0 0 75px #228DFF;
  }
}

@-webkit-keyframes neon3 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #FFDD1B, 0 0 70px #FFDD1B, 0 0 80px #FFDD1B, 0 0 100px #FFDD1B, 0 0 150px #FFDD1B;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #FFDD1B, 0 0 35px #FFDD1B, 0 0 40px #FFDD1B, 0 0 50px #FFDD1B, 0 0 75px #FFDD1B;
  }
}

@-webkit-keyframes neon4 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #B6FF00, 0 0 70px #B6FF00, 0 0 80px #B6FF00, 0 0 100px #B6FF00, 0 0 150px #B6FF00;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #B6FF00, 0 0 35px #B6FF00, 0 0 40px #B6FF00, 0 0 50px #B6FF00, 0 0 75px #B6FF00;
  }
}

@-webkit-keyframes neon5 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #FF9900, 0 0 70px #FF9900, 0 0 80px #FF9900, 0 0 100px #FF9900, 0 0 150px #FF9900;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #FF9900, 0 0 35px #FF9900, 0 0 40px #FF9900, 0 0 50px #FF9900, 0 0 75px #FF9900;
  }
}

@-webkit-keyframes neon6 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #ff00de, 0 0 70px #ff00de, 0 0 80px #ff00de, 0 0 100px #ff00de, 0 0 150px #ff00de;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #ff00de, 0 0 35px #ff00de, 0 0 40px #ff00de, 0 0 50px #ff00de, 0 0 75px #ff00de;
  }
}
/*glow for mozilla*/

@-moz-keyframes neon1 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #FF1177, 0 0 70px #FF1177, 0 0 80px #FF1177, 0 0 100px #FF1177, 0 0 150px #FF1177;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #FF1177, 0 0 35px #FF1177, 0 0 40px #FF1177, 0 0 50px #FF1177, 0 0 75px #FF1177;
  }
}

@-moz-keyframes neon2 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #228DFF, 0 0 70px #228DFF, 0 0 80px #228DFF, 0 0 100px #228DFF, 0 0 150px #228DFF;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #228DFF, 0 0 35px #228DFF, 0 0 40px #228DFF, 0 0 50px #228DFF, 0 0 75px #228DFF;
  }
}

@-moz-keyframes neon3 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #FFDD1B, 0 0 70px #FFDD1B, 0 0 80px #FFDD1B, 0 0 100px #FFDD1B, 0 0 150px #FFDD1B;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #FFDD1B, 0 0 35px #FFDD1B, 0 0 40px #FFDD1B, 0 0 50px #FFDD1B, 0 0 75px #FFDD1B;
  }
}

@-moz-keyframes neon4 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #B6FF00, 0 0 70px #B6FF00, 0 0 80px #B6FF00, 0 0 100px #B6FF00, 0 0 150px #B6FF00;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #B6FF00, 0 0 35px #B6FF00, 0 0 40px #B6FF00, 0 0 50px #B6FF00, 0 0 75px #B6FF00;
  }
}

@-moz-keyframes neon5 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #FF9900, 0 0 70px #FF9900, 0 0 80px #FF9900, 0 0 100px #FF9900, 0 0 150px #FF9900;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #FF9900, 0 0 35px #FF9900, 0 0 40px #FF9900, 0 0 50px #FF9900, 0 0 75px #FF9900;
  }
}

@-moz-keyframes neon6 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #ff00de, 0 0 70px #ff00de, 0 0 80px #ff00de, 0 0 100px #ff00de, 0 0 150px #ff00de;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #ff00de, 0 0 35px #ff00de, 0 0 40px #ff00de, 0 0 50px #ff00de, 0 0 75px #ff00de;
  }
}
/*glow*/

@keyframes neon1 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #FF1177, 0 0 70px #FF1177, 0 0 80px #FF1177, 0 0 100px #FF1177, 0 0 150px #FF1177;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #FF1177, 0 0 35px #FF1177, 0 0 40px #FF1177, 0 0 50px #FF1177, 0 0 75px #FF1177;
  }
}

@keyframes neon2 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #228DFF, 0 0 70px #228DFF, 0 0 80px #228DFF, 0 0 100px #228DFF, 0 0 150px #228DFF;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #228DFF, 0 0 35px #228DFF, 0 0 40px #228DFF, 0 0 50px #228DFF, 0 0 75px #228DFF;
  }
}

@keyframes neon3 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #FFDD1B, 0 0 70px #FFDD1B, 0 0 80px #FFDD1B, 0 0 100px #FFDD1B, 0 0 150px #FFDD1B;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #FFDD1B, 0 0 35px #FFDD1B, 0 0 40px #FFDD1B, 0 0 50px #FFDD1B, 0 0 75px #FFDD1B;
  }
}

@keyframes neon4 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #B6FF00, 0 0 70px #B6FF00, 0 0 80px #B6FF00, 0 0 100px #B6FF00, 0 0 150px #B6FF00;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #B6FF00, 0 0 35px #B6FF00, 0 0 40px #B6FF00, 0 0 50px #B6FF00, 0 0 75px #B6FF00;
  }
}

@keyframes neon5 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #FF9900, 0 0 70px #FF9900, 0 0 80px #FF9900, 0 0 100px #FF9900, 0 0 150px #FF9900;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #FF9900, 0 0 35px #FF9900, 0 0 40px #FF9900, 0 0 50px #FF9900, 0 0 75px #FF9900;
  }
}

@keyframes neon6 {
  from {
    text-shadow: 0 0 10px #fff, 0 0 20px #fff, 0 0 30px #fff, 0 0 40px #ff00de, 0 0 70px #ff00de, 0 0 80px #ff00de, 0 0 100px #ff00de, 0 0 150px #ff00de;
  }
  to {
    text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #fff, 0 0 20px #ff00de, 0 0 35px #ff00de, 0 0 40px #ff00de, 0 0 50px #ff00de, 0 0 75px #ff00de;
  }
}
/*REEEEEEEEEEESPONSIVE*/

@media (max-width: 650px) {
  #container {
    width: 100%;
  }
  p {
    font-size: 3.5em;
  }
}

Feito isso salve, caso queira ver como fica online clique aqui