Wide ads are not displayed proprerly

Hi guys, and ladies 🙂

I am trying to import Google ads to my blog and I wanted to use the wide one. (728*90)px.

As you can see from my homepage http://www.fizikcell.com , the ads are a little oversized for the main page.

How can i modify the page width? I searched the forum and found out it is to be modified from the CSS stylesheet, however I couldn’t find any relative information probably because of my theme.

I found out that the site width is 940 px. but I don’t have any idea how it is divided for the content section and widget section.
I just would like to increase the width of content section a little without making the widget section smaller.

any support will be greatly appreciated.

Thanks in advance

[please don’t bump]