title: Add centered box in html
body: <p>I tried adding a centered box in html/css using a div and specifying a class for it. I then specified the height and width for the class and set the margin for 0 auto; however all I am getting is a white rectangle that spans the entire width of my page in the top, not a centered box. My css is:</p>
  
  <pre><code>    .rectangle {
      height: 700px;
      width: 700px;
      margin: 0 auto;
      }
  </code></pre>
  
  <p>Any insight is appreciated. Thanks</p>