JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="clear-1">
<li></li>
<li></li>
</ul>
<ul id="clear-2">
<li></li>
<li></li>
</ul>

CSS

#clear-1{
position:relative;
overflow:hidden;
background-color:#f00;
margin:0 0 10px;
}

#clear-2{
background-color:#f0f;
zoom:1;
position:relative;
margin:0 0 10px;
}
#clear-2:after{
content:".";
display:block;
font-size:0;
line-height:0;   
height:0;
overflow:hidden;
text-indent:-9000px;
clear:both;
}

li{
float:left;
width:20px;
height:20px;    
background-color:#0f0;
margin:0 10px 0 0;
}