Problem with different margins when changed width of sideboxes

[parsek]

Hi,
I have ZenCart 1.3.0.2

I used Admin panel to change the width for Right Boxes to 185px and for Left Boxes to 135 px.

I set .mainWrapper in _new {width: 800px;} to the width of the header image header_bg.jpg

and .centershop in _original {width:100%; }

but margin on the right hand site of the Right Boxes are much larger then margin on the left hand site of the Left Boxes. What I can do to even out?

Thank you,
Inna