Live Example: (Read the CSS Newbie article)

Source Code: (Save the Source)

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>CSS Newbie Example: Test for Placeholder Support</title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script>
// This adds 'placeholder' to the items listed in the jQuery .support object. 
jQuery(function() {
   jQuery.support.placeholder = false;
   test = document.createElement('input');
   if('placeholder' in test) jQuery.support.placeholder = true;
});
// This adds placeholder support to browsers that wouldn't otherwise support it. 
$(function() {
   if(!$.support.placeholder) { 
      var active = document.activeElement;
      $(':text').focus(function () {
         if ($(this).attr('placeholder') != '' && $(this).val() == $(this).attr('placeholder')) {
            $(this).val('').removeClass('hasPlaceholder');
         }
      }).blur(function () {
         if ($(this).attr('placeholder') != '' && ($(this).val() == '' || $(this).val() == $(this).attr('placeholder'))) {
            $(this).val($(this).attr('placeholder')).addClass('hasPlaceholder');
         }
      });
      $(':text').blur();
      $(active).focus();
      $('form:eq(0)').submit(function () {
         $(':text.hasPlaceholder').val('');
      });
   }
});
</script>
<style>
body {
   font: x-large/1.4 Georgia, "Times New Roman", Times, serif;
   text-align: center; }
#infobox {
   width: 400px;
   margin: 20px auto;
   padding: 20px;
   color: #333;
   background-color: #9fe1ff;
   border: 4px solid #333;
   /* Our massive border-radius stack. */
   -moz-border-radius: 10px;
   -webkit-border-radius: 10px;
   -o-border-radius: 10px;
   -khtml-border-radius: 10px;
   border-radius: 10px;
   -moz-box-shadow: 0 0 5px #333;
}
#infobox input {
   width: 80%;
}
.hasPlaceholder {
   color: #777;
}
</style>
</head>
<body>
   <p>Test in different browsers to see the results.</p>
   <p><a href="/test-for-border-radius-support/">View the original article.</a></p>
   <div id="infobox">
      <input type="text" placeholder="This works in all modern browsers!" />   
   </div>
</body>
</html>