title: HTML/CSS: About <div id> and <div class> with a wrapper
body: <p>am totally new in HTML and Im wondering about the wrapper thing. Can you tell me why there is first "div <strong>id</strong>" and then in the subcode "div <strong>class</strong>="wrapper" ? Could I replace the <strong>id</strong> with <strong>class</strong> to have the same effect, and vice versa? I mean why is it that first comes  and then ?</p>
  
  <pre><code>    &lt;header&gt;
          &lt;div class="Wrapper"&gt;
              &lt;h1&gt;&lt;/h1&gt;
              &lt;nav&gt;&lt;/nav&gt;
          &lt;/div&gt;
      &lt;/header&gt;
  
  
      &lt;div **id**="heroImage"&gt;
          &lt;div **class**="Wrapper"&gt;
              &lt;h2&gt;&lt;/h2&gt;
              &lt;a&gt;&lt;/a&gt;
          &lt;/div&gt;
      &lt;/div&gt;
  
  
      &lt;div id="features"&gt;
          &lt;ul&gt;
              &lt;li&gt;&lt;/li&gt;
              &lt;li&gt;&lt;/li&gt;
              &lt;li&gt;&lt;/li&gt;
          &lt;/ul&gt;
      &lt;/div&gt;
  
  
      &lt;div id="primaryContent"&gt;
          &lt;article&gt;&lt;/article&gt;
      &lt;/div&gt;
  
  
      &lt;div id="secondaryContent"&gt;
          &lt;article&gt;&lt;/article&gt;
          &lt;article&gt;&lt;/article&gt;
      &lt;/div&gt;
  </code></pre>