title: insert/remove HTML content between div tags
body: <p>how can I insert some HTML code between <code>&lt;div id="mydiv"&gt;...&lt;/div&gt;</code> using javascript?</p>
  
  <p>Ex: <code>&lt;div id="mydiv"&gt;&lt;span class="prego"&gt;Something&lt;/span&gt;&lt;/div&gt;</code> its about 10 lines of html of most. thank you</p>