JSFiddle - React, Tailwind, and code Playground

HTML

<div id="tab">
    <h1>Заголовок</h1>
</div>
<div id="content">Содержимое блока</div>
<div id="green">&nbsp;</div>

CSS

#tab{
    border-radius:10px 10px 0 0;
    display:block;
    min-width:125px;
    width:20%;
    height:26px;
    text-align:center;
    box-shadow: 0 0 10px rgba(0,0,0,0.5);
    -moz-box-shadow: 0 0 10px rgba(0,0,0,0.5);
    -webkit-box-shadow: 0 0 10px rgba(0,0,0,0.5);
    background:#c9e39c;
    padding-top:5px;
}

h1{
    font-size:16px;
    font-family:Tahoma;
    font-weight:bold;
}

#content{
    border-radius:0 0 10px 10px;
    width:100% - 15px;
    height:150px;
    box-shadow:0 0 10px rgba(0,0,0,0.5);
    -moz-box-shadow:0 0 10px rgba(0,0,0,0.5);
    -webkit-box-shadow:0 0 10px rgba(0,0,0,0.5);
    background:#c9e39c;
    min-width:300px;
    padding:15px;
}

#green{
    background:#c9e39c;
    display:block;
    min-width:125px;
    width:20%;
    margin-top:-190px;
}