First step is to create the form. I usually have all my forms inside a list:

UPDATE: It's necessary to turn off the "autocomplete" so the inputs don't get messed up.

markup
<form action="">
  <ul>
   <li>
    <label for="username">Username</label>
    <input id="username" type="text" autocomplete="off" />
   </li>
   <li>
    <label for="password">Password</label>
    <input id="password" type="password" autocomplete="off" />
   </li>
   <li>
    <input type="submit" value="login" />
   </li>
  </ul>
</form>

Don't forget the "for" attribute, the script will rely on it. Go ahead and add the following CSS:

CSS
form li { position: relative; }
label {
  position: absolute;
  top: 5px; // adjust as needed
  left: 5px;
}
//remove absolute position if the label comes after
//the input. Eg. a checkbox with a text next to it
input + label { position: static; }

Now the final touch. With some jQuery magic, lets make the label disappear on focus.

jQuery
//loop through all text inputs, password inputs and textarea
var inputs = $('input[type="text"], textarea, input[type="password"]');

// remove label on focus
inputs.focus(function(){
  $('label[for="'+$(this).attr('id')+'"]').hide();
});
inputs.blur(function(){
  var that = $(this);
  if (that.val() == ""){
    $('label[for="'+that.attr('id')+'"]').show();
  }
});
inputs.blur();

Demo

Let's start by creating the following markup:

Markup
<a href="http://www.example.com" class="tooltip">
 My Link 
 <span>Cool tooltip<small></small></span>
</a>

CSS
.tooltip { position: relative; }
.tooltip span {
  position: absolute;
  right: 0;
  top: -35px;
  display: none;
  min-width: 50px;
  padding: 3px 8px;
  white-space: nowrap;
  font-size: 11px;
  text-align: center;
  background-color: rgba(0,0,0,.8);
  -webkit-border-radius: 5px;
  -moz-border-radius: 5px;
}
.tooltip span small {
  position: absolute;
  right: 10px;
  bottom: -6px;
  border-top: 6px solid rgba(0,0,0,.8);
  border-left: 6px solid transparent;
}
.tooltip:hover span { display: block; }

As I mentioned in a previous article, IE doesn't support RGBa. Adding the following styles, wrapped in a conditional comment, will make it work.

IE CSS
.tooltip span { background-color: #000; }
.tooltip span small { border-top: 6px solid #000; }
IE 6 Tooltip Arrow Fix
*html .tooltip span small { 
  border-left: 6px solid #363636; /* Match the color of the background */
} 

For more info about creating speech bubble using only CSS, go to DeSandro's tutorial on creating speech bubble.

Demo

My Link Cool Tooltip
Long Tip Test Very Long Tooltip Test Very Long Tooltip Test

Keith's Example using jQuery:
jQuery(function($) {
$('body').addClass('hasJS');
});

CSS
.hasJS .module {
display: none;
}

Why add a class if JavaScript is enabled?

Although the majority of desktop users have JavaScript enabled, mobile is one of the most used platforms to surf the web. Some mobile browsers don't support JavaScript. Keep in mind that search engines don't run JavaScript, so NEVER add important content using JavaScript.

My current project at work requires the content to be rendered for both enabled and disabled JavaScript browsers. I did a bit of research and found that most websites/solutions add the hasJS class to the body after the DOM is loaded. My first thought was, if the class gets added after the DOM is loaded, a shift on the page will occur providing a bad user experience. Yahoo was a site I researched and they have, IMHO, the cleverest solution of them all. They add the class to the HTML element instead of the BODY element. The first script block on the page to be loaded adds the hasJS class without dependency on libraries. Note: Yahoo uses another class name "jsenabled".

You might be asking why add the class to the HTML element? I think it makes more sense because the BODY is the beginning of the content. This means that everything after the body is "visible" to the user and blocking the content with a script tag isn't a good optimization practice. Here is the code to add the hasJS class to the body:

hasJS Script Block
<script type="text/javascript">
  document.getElementsByTagName('html')[0].className = 'hasJS';
</script>

NOTE: If you already have more classes on the HTML element, use document.getElementsByTagName('html')[0].className += ' hasJS'; instead.

New Easy-Clearing
.group:after {
  content: ".";
  display: block;
  height: 0;
  clear: both;
  visibility: hidden;
}

Using conditional comments, let's add the proper code to handle IE 6 and IE 7 (IE8 supports the :after pseudo-elements; no extra code is necessary).

New Easy-Clearing for IE
/* IE6 */
* html .group { height: 1%; }

/*IE7 */
.group { min-height: 1px; }

I've been using the group class on my latest projects and I'd like to share a small tip, when clearing list items, with you.

Normally, we'd have the group class on every LI, like so:

Clearing List Items the Old Way
<ul class="comments">
  <li class="group">
    <img src="carla.jpg" alt="Carla&#x27;s Picture" />
    <p>Tiny and I miss you</p>
  </li>
  <li class="group">
    <img src="steven.jpg" alt="Steven&#x27;s Picture" />
    <p>I need a favor! It will take you 5 seconds.</p>
  </li>
  <li class="group">
    <img src="buzz.jpg" alt="Buzz&#x27;s Picture" />
    <p>I speak gibberish</p>
  </li>
</ul>

Although the markup doesn't look very bad, we can make things better by introducing a new class (groupList) and adding it to the UL.

Clearing List Items the New Way
<ul class="comments groupList">
  <li>
    <img src="carla.jpg" alt="Carla&#x27;s Picture" />
    <p>Tiny and I miss you</p>
  </li>
  <li>
    <img src="steven.jpg" alt="Steven&#x27;s Picture" />
    <p>I need a favor! It will take you 5 seconds.</p>
  </li>
  <li>
    <img src="buzz.jpg" alt="Buzz&#x27;s Picture" />
    <p>I speak gibberish</p>
  </li>
</ul>

Phew, the markup looks much cleaner! Now that we've fixed it, let's add the .groupList > li selector to the existing .group styles.

Extending .group
.groupList > li,
.group:after {
  content: ".";
  display: block;
  height: 0;
  clear: both;
  visibility: hidden;
}

Wait! How about the beloved IE?

Extending .group IE
/* IE6 */
* html .groupList li,
* html .group { height: 1%; }
* html .groupList li li { height: auto; } /* Resets nested LIs */

/*IE7 */
.group > li,
.group { min-height: 1px; }

Browser Support

• Firefox
• Safari
• Chrome
• Opera
• Internet Explore 7 & 8
• Internet Explore 6