How To Make Image Stay In Front

I have a Comodo Secure image in my left sidebar widget. If you scroll to the bottom of the page and then hover over the image, it goes behind the second footer widget. Please see screenshot.

The current code I have for that widget is Hover to see details<script language="JavaScript" type="text/javascript">
TrustLogo("/uploads/2016/11/comodo_secure_seal_113x59_transp.png", "CL1", "none":wink:;

I know that I have to put in a z-index code but am not having any success. I'm obviously doing it incorrectly. Can you tell me please how to change the above code to make the Comodo Seal stay in front when hovering.

Support access is granted. Thank you.