How to make ad Groups responsive

Hi

I inserted 2 Ad Groups below my menu at http://www.der-bank-blog.de with the following code directly in the php file:

<?php/** Ad Rotate Block unter Menu */?>
<div id=”center-ad”>
<div id=”linke_anzeige”>
<?php echo adrotate_group(4);?>
</div>
<div id=”rechte_anzeige”>
<?php echo adrotate_group(7);?>
</div>

It works fine on Desktop, but not on mobile.

The CSS is the follwoing:
/* Anzeigen unter Menu */
#center-ad
{
margin: 5px auto;
width: 1000px;
}
#linke_anzeige
{
float:left;
padding: 2px;
border-width:1px;
border-style:solid;
border-color:#000000;
width:728px;height:90px;
}
#rechte_anzeige
{
float:right;
padding: 2px;
border-width:1px;
border-style:solid;
border-color:#000000;
width:220px;height:90px;
}
.clr { clear: both; }

On mobile all ads are left and right of the Screen. What am I doing wrong?

Cheers

Hansjörg

https://wordpress.org/plugins/adrotate/