[nyols]

<style>
   h1 {
      font-size: 40px;
   }
</style>

<script>
   function fix(h1) {
      if (h1.innerHTML.length > 20)
         h1.style.fontSize = '20px';
      else if (h1.innerHTML.length > 10)
         h1.style.fontSize = '30px';
   }
</script>

<h1 onclick="fix(this);">Fix me plese</h1>
<h1 onclick="fix(this);">Fix me pleaseeeeeeeeeeeeeeeeeeeeeeeee</h1>