<p>Какой-то текст</p>
.........
<style> p { animation: blink 400ms alternate infinite; } @keyframes blink { from { opacity: 1; } to { opacity: 0; } } </style> <p>Какой-то текст</p>
<p id="blink">Some text</p> <script> setInterval(function(){ var a = document.getElementById('blink').style.opacity || 1; document.getElementById('blink').style.opacity = ((parseInt(a))?0:1); },1e3); </script>
(a?0:1)
a = 1 - a;
<p id="blink">Some text</p> <script> setInterval(function(){ blink.style.opacity = 1 - (blink.style.opacity || 1); },1e3); </script>
<p id="blink">Some text</p> <script> setInterval(function(){ blink.style.opacity ^= 1 ; },1e3); </script>