JSFiddle - React, Tailwind, and code Playground

HTML

<div id="sidebar">
            <div class="sidebar_box">
                <div class="sidebar_header">Advertisement</div>
                <img src="http://dummyimage.com/180x150/ABABAB/ddd.png" width="180" height="150" />
            </div>
        </div>

CSS

*{
    padding:0;
    margin:0;
}

img{
    border:0;
    vertical-align:top;
}

#sidebar .sidebar_box{
    width:180px;
    background:#fff;
    border:1px solid #000;
}

#sidebar .sidebar_header{
    width:180px;
    background:#ddd;
    border-bottom:1px solid #000;
}