How do I center my images in Facebox?

How do I center my images in Facebox?

I am using Facebox and the popups are centered for text but when I include
images they are not being centered on Safari and Chrome. On Firefox it's
fine.
What can I do to make it centered on Chrome and Safari?
This is how a popup with an image looks like for me:
<div id="example1" style="display:none;">
<a class="close" onclick="$.facebox.close();">
</a>
<img src="/images/ok.png" class="ok">
</div>
JQuery Trigger:
<a href="#example1" class="some_link" rel="facebox">View Example</a>