Can't get AdSense Banner to Center Correctly

Been working on adding an AdSense banner to my Child Theme (Twenty Twelve). Want to add an adsense banner above my header. Added this code to my header.php file:

<div class="header-adsense">
My Adsense Code
	</div>

And then I added this code to my style.css file:

.header-adsense {
	width: 100%; text-align: center; margin-top: 10px; margin-bottom: -35px;
}

It looks beautiful on my local site (I even checked in three different browsers) but when I upload to my live site, this is what I get. Upper left-hand corner of my site.

Can anyone help? Much appreciated.