html, body			{ width: 100%; height: 100%; margin: 0; padding: 0; }
div				{ width: 100%; float: left; box-sizing: border-box; overflow: hidden; }

#mainContainer   div		{ margin-left: 4%; width: 20%; border: 1px solid #ff0000; }
#mainContainer > div		{ width: 100%; margin: 30px 0px 0px 0px; border: 0; }