Give the main body percentage padding

Im not sure if what im asking is possible, so i would like to hear some ideas just to be sure.

When the site is in a minimized window or a smaller inch screen it comes up like in picture A
but when view in it on full screen at a bigger screen it comes up like picture B.

My question is if & how can i keep the same view (picture A) no mater what the size of the screen is.

This would require re-development of entire template's layout which is defined in CSS file. It would be required to use width values in percents rather than in pixels. This could make problems though, in example when visitor's screen is too wide. Also, all inner elements, including images must be in percents which is currently not possible for Hot Effects Rotator module.

Regards
Milos