float:left だと難しい理由

by Takayuki Shimada

HTML

<div class="grid">
    <div class="grid__unit"><div class="unit-inner">float 1<br/>float 1<br/>float 1</div></div>
    <div class="grid__unit"><div class="unit-inner">float 2<br/>float 2</div></div>
    <div class="grid__unit"><div class="unit-inner">float 3</div></div>
    <div class="grid__unit"><div class="unit-inner">float 4</div></div>
    <div class="grid__unit"><div class="unit-inner">float 5</div></div>
    <div class="grid__unit"><div class="unit-inner">float 6</div></div>
</div>

CSS

html {
    background-color: gray;
}
body {
    width: 80%;
    margin: 0 auto;
    background-color: #fff;
}
.grid {
    margin-top: -10px;
    margin-left: -20px;
}
.grid:after {
    content: "";
    display: block;
    clear: both;
}
.grid__unit {
    float: left;
    width: 33.33%;
    padding-top: 10px;
    padding-left: 20px;
    box-sizing: border-box;
}
.unit-inner {
    padding: 5px;
    background-color: #ccc;
}