Question

How could I change this grid layout so that the second row of blocks sit just below the corresponding block above it instead of forming a completely new row?

http://jsfiddle.net/AndyMP/wSvrN/

body {
    margin-left: 0px;
    margin-top: 0px;
    margin-right: 0px;
    margin-bottom: 0px;
}
#container {
    position: absolute;
    width: 60%;
    left: 50%;
    margin-left: -30%;
    border: 1px dotted #333;
    padding: 20px;
}
.box1 {
    position: relative;
    float: left;
    width: 100px;
    height: 150px;
    background: #666;
    margin: 0 15px 15px 0;
}
.box2 {
    position: relative;
    float: left;
    width: 100px;
    height: 200px;
    background: #666;
    margin: 0 15px 15px 0;
}
.box3 {
    position: relative;
    float: left;
    width: 100px;
    height: 100px;
    background: #666;
    margin: 0 15px 15px 0;
}

HTML

<div id="container">

    <div class="box1"></div>
    <div class="box3"></div>
    <div class="box1"></div>
    <div class="box2"></div>
    <div class="box3"></div>
    <div class="box2"></div>
    <div class="box3"></div>
    <div class="box2"></div>
    <div class="box1"></div>
    <div class="box1"></div>
    <div class="box3"></div>
    <div class="box2"></div>

</div>

Answer 1

You can not achieve this with Pure CSS. You have to use http://masonry.desandro.com/ for this.