Another solution: You can use percentage units for margins as well as sizes. For example:
.fullWidthPlusMargin { width: 98%; margin: 1%;}The main issue here is that the margins will increase/decrease slightly with the size of the parent element. Presumably the functionality you would prefer is for the margins to stay constant and the child element to grow/shrink to fill changes in spacing. So, depending on how tight you need your display to be, that could be problematic. (I'd also go for a smaller margin, like 0.3%).
