<div class="container"> <div class="B B1">B1</div> <div class="B B2">B2</div> <div class="B B3">B3</div> </div>
.container { display: -webkit-flex; display: flex; width: 500px; height: 150px; background-color: #eee; } .B { width: 100px; height: 100px; } .B1{ background-color:rgba(255,255,0,.5); -webkit-flex-grow:1; -moz-flex-grow:1; flex-grow:1; } .B2{ background-color:rgba(255,0,255,.5); -webkit-flex-grow:2; -moz-flex-grow:2; flex-grow:2; } .B3{ background-color:rgba(0,255,255,.5); }