The How and Why of Clearing Floats

You’ve heard of “clearing floats”, but do you really understand it? The whole problem is that floated objects do not add to the height of the object the reside in properly. As you can see below, these divs with the class “floated_box” are within the div “main_container”, yet on the page they are outside that container div.

#main_container {
 width: 400px;
 margin: 20px auto;
 border: 2px solid #cccccc;
 padding: 5px;
}

.floated_box {
 float: left;
 width: 100px;
 height: 100px;
 border: 1px solid #990000;
 margin: 10px;
}

<div id="main_container">
 <p>Some content.</p>
 <div class="floated_box"></div>
 <div class="floated_box"></div>
 <div class="floated_box"></div>
 <div class="floated_box"></div>
 <div class="floated_box"></div>
</div>

All we need to do is clear the float, and this entire problem goes away. Put this empty div AFTER your last floated object:

<div style="clear: both;"></div>

And you get this:

This fix does add some useless markup, which is antithetical to the tao of CSS, but it’s an easy cross-browser fix that won’t let you down.