Make children divs the height of tallest child

Answer 1

Another solution is to use flexbox: http://jsfiddle.net/7m4f7/4/

.item {
    background: rgba(0,0,0,0.1);
    -webkit-box-flex: 1;
    -moz-box-flex: 1;
    -webkit-flex: 1;
    -ms-flex: 1;
    flex: 1;
}

.row {
    border: 1px solid red;
    display: -webkit-box;
    display: -moz-box;
    display: -webkit-flexbox;
    display: -ms-flexbox;
    display: -webkit-flex;
    display: flex;
}

However, support is limited (but getting better!) See http://caniuse.com/flexbox

Otherwise you need to use javascript to set the heights manually.