title: default body margin, I didn't set, but it does have default value 8px, how can get this value?
body: <pre><code>    &lt;style type="text/css"&gt;
          fieldset {
              border: solid 1px orange
          }
          .label {
              font-family: Arial;
              font-size: 12px;
              font-weight: bold
          }
          .groupName {
              font-family: Segoe UI;
              font-size: 16px;
              color: Gray
          }
      &lt;/style&gt;
  
      &lt;script type="text/javascript" src="libs/json2.js"&gt;&lt;/script&gt;
      &lt;script type="text/javascript" src="libs/jquery.js"&gt;&lt;/script&gt;
      &lt;script type="text/javascript" src="libs/sap.common.globalization.js"&gt;&lt;/script&gt;
      &lt;script type="text/javascript" src="libs/sap.riv.base.js" base-url="modules/"&gt;&lt;/script&gt;
      &lt;script type="text/javascript" src="modules/main.js"&gt;&lt;/script&gt;
      &lt;script type="text/javascript" src="libs/sap.riv.themes.js"&gt;&lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;div id="chart" style="width: 600px; height: 400px; background-color: #ffffff"&gt;&lt;div id="0" style="position: absolute; font-size: 10px; box-sizing: border-box; overflow-x: visible; overflow-y: visible; left: 8px; top: 8px; width: 600px; height: 400px; "&gt;` 
  </code></pre>
  
  <p>In chrome I can see</p>
  
  <pre><code> body{
   display:block;
   margin: 8px;
  }
  </code></pre>
  
  <p>I use document.getElementsByTagName('body').style but get nothing.</p>
  
  <p>my first div located at top&amp;left: 8px of the html body.</p>
  
  <p>But it does have margin, how could I get this default margin value?</p>