How Open the dropdown menu pages in the same page

Question

When I click on the item Home,

<li><a href="test.html" target="secondo-menu">Home</a></li>

I wish the test.html page is opened in the same page on

<div id="secondo-menu">

instead of as happens now on a new page.

<div id="drop-menu">
<ul id="menu">
<li><a href="test.html" target="secondo-menu">Home</a></li>
<li><a href="#">Categories</a>
<ul>
<li><a href="#">CSS</a></li>
<li><a href="#">Graphic design</a></li>
<li><a href="#">Development tools</a></li>
<li><a href="#">Web design</a></li>
</ul>
 </li>
 <li><a href="#">Work</a>
<ul>
<li><a href="#">About</a></li>
<li><a href="#">Contact</a></li>
</ul>
</div>
<div id="secondo-menu">
<iframe src="http://www.example.com" height="100%" width="100%">
  Contenuto alternativo per i browser che non leggono gli iframe.
</iframe></div>