Click a button with no ID or Name

I need to fire the onclick event for a link but I have no way to identify the object.

<div id="button">
	 <a href="" onclick="some_javascript_here">
		  <img alt="Add Account" src="images/add_account_button_blue.jpg">
	 </a>
</div>

As you can see, I can identify the parent element in the DOM (id="button") but I can't find a way to use that information to target the daughter <a> tag.

Any ideas?