diff --git a/user_guide/index.html b/user_guide/index.html
index 2fb0681..2d08fcc 100644
--- a/user_guide/index.html
+++ b/user_guide/index.html
@@ -24,7 +24,7 @@
 
 <!-- START NAVIGATION -->
 <div id="nav"><div id="nav_inner"><script type="text/javascript">create_menu('null');</script></div></div>
-<div id="nav2"><a name="top"></a><a href="javascript:void(0);" onclick="myHeight.toggle();"><img src="images/nav_toggle.jpg" width="153" height="44" border="0" title="Toggle Table of Contents" alt="Toggle Table of Contents" /></a></div>
+<div id="nav2"><a name="top"></a><a href="javascript:void(0);" onclick="myHeight.toggle();"><img src="images/nav_toggle_darker.jpg" width="154" height="43" border="0" title="Toggle Table of Contents" alt="Toggle Table of Contents" /></a></div>
 <div id="masthead">
 <table cellpadding="0" cellspacing="0" border="0" style="width:100%">
 <tr>