Ad injection support

Somehow, when I insert ads with the plugin Ad Injection into the content, there is a blank line and as well a margin around the ads, which are filled with yellow background color! This doesn’t happen with any other theme where I use Ad injection, so I think it’s caused by the theme!

Any idea where I can change this? I didn’t find anything in the CSS file, not even the color code which is displayed…

Any help is highly appreciated!

the website is nikbender.com