glow effect css

CSS

.neon {
  -webkit-animation: glow 1.2s ease-in-out infinite alternate;
  -moz-animation: glow 1.2s ease-in-out infinite alternate;
  animation: glow 1.2s ease-in-out infinite alternate;
}

@-webkit-keyframes glow {
  from {
    -webkit-filter: drop-shadow(4px 4px 5px rgba(161,11,150,0.2));
    filter: drop-shadow(4px 4px 5px rgba(161,11,150,0.2));
  }
  to {
    -webkit-filter: drop-shadow(4px 4px 5px rgba(161,11,150,1)); 
    filter: drop-shadow(4px 4px 5px rgba(161,11,150,1)); 
  }
}
    
@-moz-keyframes glow {
  from {
    -moz-filter: drop-shadow(4px 4px 5px rgba(161,11,150,0.2));
    filter: drop-shadow(4px 4px 5px rgba(161,11,150,0.2));
  }
  to {
    -moz-filter: drop-shadow(4px 4px 5px rgba(161,11,150,1));
    filter: drop-shadow(4px 4px 5px rgba(161,11,150,1));
  }
}

HTML

<img class="neon" src="http://greckzero.com/sources/key.png" alt="Key" />
<p class="neon">Glow Effect Text</p>

Demo