title: CSS Put Div Tag at top of page without space
body: <p>I want to put a div tag with id "wrapper" at top of page, but the problem is
  that there is a white space between the div tag "wrapper is yellow color"<br>
  and the top of page.</p>
  
  <p>My question is how can I remove the white space between the div tag and the top 
  of page?</p>
  
  <p>Here is my code</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>    &lt;!DOCTYPE html&gt;
      &lt;html&gt;
       &lt;head&gt;
       &lt;style type='text/css'&gt;
       body {
       margin: 0;
       padding:0;
       }  
       
       #wrapper {
       width:1000px;
       text-align:center;
       margin-right:auto;
       margin-left:auto;
       margin-top:0px;
       background-color: yellow;
       padding:0px;
       }
       &lt;/style&gt;
       &lt;/head&gt;
  
       &lt;body&gt;
        &lt;div id="wrapper"&gt;
         Testing
        &lt;/div&gt;
       &lt;/body&gt;
      &lt;/html&gt;</code></pre>
  </div>
  </div>
  </p>