blink.css

blink {
    -webkit-animation: blink .75s linear infinite;
    -moz-animation: blink .75s linear infinite;
    -ms-animation: blink .75s linear infinite;
    -o-animation: blink .75s linear infinite;
    animation: blink .75s linear infinite;
}

@-webkit-keyframes blink {
    0% { opacity: 1; }
    80% { opacity: 1; }
    80.01% { opacity: 0; }
    100% { opacity: 0; }
}

@-moz-keyframes blink {
    0% { opacity: 1; }
    80% { opacity: 1; }
    80.01% { opacity: 0; }
    100% { opacity: 0; }
}

@-ms-keyframes blink {
    0% { opacity: 1; }
    80% { opacity: 1; }
    80.01% { opacity: 0; }
    100% { opacity: 0; }
}

@-o-keyframes blink {
    0% { opacity: 1; }
    80% { opacity: 1; }
    80.01% { opacity: 0; }
    100% { opacity: 0; }
}

@keyframes blink {
    0% { opacity: 1; }
    80% { opacity: 1; }
    80.01% { opacity: 0; }
    100% { opacity: 0; }
}

default.html

<blink>Some blinking text</blink>

jquery.html

<script type="text/javascript">
  setInterval(jQuery('blink').toggle, 700);
</script>
<blink>Some blinking text</blink>

niceblink.css

blink {
    animation: blink 1s steps(5, start) infinite;
}
@keyframes blink {
    to {
        visibility: hidden;
    }
}

purejs.html

<script type="text/javascript">
  // Taken from: https://en.wikipedia.org/wiki/Blink_element
  function blink() {
    var blinks = document.getElementsByTagName('blink');
    for (var i = blinks.length - 1; i >= 0; i--) {
      var s = blinks[i];
      s.style.visibility = (s.style.visibility === 'visible') ? 'hidden' : 'visible';
    }
    window.setTimeout(blink, 1000);
  }
  if (document.addEventListener) document.addEventListener("DOMContentLoaded", blink, false);
  else if (window.addEventListener) window.addEventListener("load", blink, false);
  else if (window.attachEvent) window.attachEvent("onload", blink);
  else window.onload = blink;
</script>
<blink>Some blinking text</blink>

viacss.html

/* Specified in CSS 2.1 */
<span style="text-decoration: blink;">Some blinking text</span>