Ad in header

I’ve been working on this for some time now and still can’t get it to work correctly.

I have my div in the header:

<div id=”header-right”>
<?php if (function_exists('dfrads')) { echo dfrads('5537092'); } ?>
</div>

and I have my style in styles.css

#headerright {
float: right;
margin: 15px 10px 0px 0px;
width: 720px;
height: 90px;
padding: 0px;
border: 0px;
}

but I can’t seem to get it to recognize the style and float it right. I can align it when I inspect the element fine but there there is no line to replace or add to in the style.css…

Any help would make my day. Thanks in advance!