title: Adding a new checkbox makes the other checkboxes unchecked
body: <p>When I add a new checkbox, old checkboxes are set unchecked (even when they were checked). How can I solve it?</p>
  
  <p>Here there is my code:</p>
  
  <pre><code>&lt;%@ page language="java" contentType="text/html; charset=ISO-8859-1"
      pageEncoding="ISO-8859-1"%&gt;
  &lt;!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"&gt;
  &lt;html&gt;
  &lt;head&gt;
  &lt;meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"&gt;
  &lt;title&gt;Insert title here&lt;/title&gt;
  &lt;script type="text/javascript"&gt;
  function zaza() {
      document.body.innerHTML+=
          '&lt;input type="checkbox" name="vehicle" value="Bike"&gt; I have a bike&lt;br&gt;';
  }
  
  &lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
  &lt;input type="checkbox" name="vehicle" value="Bike"&gt; I have a bike&lt;br&gt;
  &lt;p onclick="zaza()"&gt;add&lt;/p&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>