Please help (css+html)

Hello
I am creting a wordpress website.
My website:
http://www.decorareprojetar.com.br/
My client said:
the middle divs are ok, but don't give them a set witdh. Instead just let them be, give them a margin right to get the with spacing.
Images need to be resaved as black and white / side by side with color, so on mouse over I just slide the background position instead of changing the source of the image (which results in a flicker.
How can I do this?
Thanks.
Please help (css+html)

See original post by alkantenik