[How To Serve Responsive Ads?]

Maybe it's not too late, I just want to share my trick.

Just put the invocation code in an element, and modify the width/height on parsing.

<div id="some-id">
    <script type='text/javascript'>
        // invocation code here
    </script><noscript><!-- bla bla --></noscript>
</div>
<script>
    $(document).ready(function () {
        var img = $('#some-id').find('img');
        if (typeof (img) !== 'undefined' && img.length > 0) {
            $(img)
                    .removeAttr('width')
                    .removeAttr('height')
                    .addClass('img-responsive'); // eg: twitter bootstrap
        }
    });
</script>

On this case, I didn't care about the downloading size, but only how it's being presented.

Still, the original width + height should exactly match with the zone's size.