Centering Ads in My Blog Sidebar

I realize that this topic has been covered here before but I’ve tried all of the solutions suggested and am still not able to center Adsense or Lijit ads in my sidebar: PepperDesignBlog.com

Here are some solutions that I have tried:

<div id=”adsenseAd”><script type=”text/javascript” src=”https://ap.lijit.com/www/delivery/fpi.js?z=247744&u=mspenla&width=300&height=250″></script></div&gt;
(and then adding #adsenseAd { text-align: center; } to the bottom of my css stylesheet)

<div style=”margin:25px;”>
<script async src=”https://ap.lijit.com/www/delivery/fpi.js?z=247744&u=mspenla&width=300&height=250″&gt;
</script>
</div>

<center>
<script async src=”https://ap.lijit.com/www/delivery/fpi.js?z=247744&u=mspenla&width=300&height=250″&gt;

</center>

<div align=”center”></div> (instead of above)

I am learning by trial and error so any help is appreciated! Thanks in advance.