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              <h1>Classes and IDs</h1>

<p>Say we have a notification to style, with an id of <code>notification</code>.<p>

<div id="notification">
  This has an <strong>id</strong> of <code>notification</code>, so it is selected in CSS with <code>#notification</code>. Check it out.
</div>

<p>But what if we have many messages on the page which are meant to look similar?</p>

<div class="message">
  This is in an element with a <strong>class</strong> of <code>message</code>, so it can be selected in CSS with <code>.message</code>.
</div>

<div class="message">
  This is in another element with a <strong>class</strong> of <code>message</code>, so it gets styled too.
</div>

<div class="message">
  A third element with a <strong>class</strong> of <code>message</code>, for good measure. One CSS selector styles all of these.
</div>

<h2>IDs are singular, Classes are plural</h2>

<p>An ID is meant to be used only once in a given HTML document. A given element can have only one ID.</p>

<p>A class can be reused as many times as needed in a given HTML document. A given element can have multiple classes.</p>

<h2>Using Multiple Classes</h2>

<p>An element can be given multiple classes, separated by spaces, such as <code>class="foo bar baz"</code>.</p>

<div class="message error">
  This has <code>class="message error"</code>, meaning it has two classes: <code>message</code> and <code>error</code>. It will get styles from <code>.message</code> and <code>.error</code>. The styles for <code>.error</code> override the default styles, which we achieve by placing them after the styles for <code>.message</code>.
</div>

<h2>Your Turn</h2>

<p>Add a new element to the page below the error message, that will serve as a success message, and style it to be green.</p>
            
          
!
            
              body {
  font-family: sans-serif;
  line-height: 1.4;
  margin: 30px;
}

#notification {
  background: #EEE;
  padding: 10px;
  border: 1px solid #CCC;
}

.message {
  background: #FFE;
  padding: 15px;
  border: 2px solid #CCB;
  margin: 10px 0;
}

.error {
  background: #FEE;
  border-color: #C66;
}

code {
  background: rgba(0,0,0,.05);
  padding: 1px 4px;
  border: 1px solid rgba(0,0,0,.2);
  border-radius: 4px;
  margin: 0 1px;
  white-space: nowrap;
}
            
          
!
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