.wrapper { width: 960px; /* Some arbitrary bounding. 960px is usually the width of fixed-width layouts. */ } .three-column { /* width: 33%; */ width: 310px; /* 960px/3 = 320px, 320px-15px (5px left padding + 5px right padding) = 310px */ height: 200px; /* Stick in an arbitrary height for display purposes. */ float: left; background: #f00; /* Red, again for display purposes */ padding: 0 5px; } .three-column:first-child { background: #0f0; /* Green, to show the column differences */ } .three-column:last-child { background: #00f; /* Blue, to show the column differences */ }