JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE HTML>
<html lang="en-US">
    <head>
        <meta charset="UTF-8">
        <title>Задание 3</title>
    </head>
    <body>
        <div class="wrapper">
            <div class="inner">
                <h1>Заголовок</h1>  
                <p>Содержимое</p>  
            </div>
        </div>
    </body>
</html>

CSS

body {
    background: url(http://htmlbook.ru/example/images/redline.png); 
    padding: 11px;  
    font-family: Arial, sans-serif;
}

.wrapper {
    padding: 7px;
    background: -moz-linear-gradient(top, rgba(87, 183, 162, 0.5), rgba(45, 92, 81, 0.5));
    background: -webkit-gradient(linear,left top,left bottom, color-stop(0, rgba(87, 183, 162, 0.5)), color-stop(1, rgba(45, 92, 81, 0.5)));
    background: linear-gradient(top, rgba(87, 183, 162, 0.5), rgba(45, 92, 81, 0.5));
    
    border: 2px solid #004c3b;
    
    -moz-border-radius: 5px;
    -webkit-border-radius: 5px;
    border-radius: 5px;   
    filter:progid:DXImageTransform.Microsoft.Gradient(GradientType=0, StartColorStr='#8057b7a2', EndColorStr='#802d5c51');
}

.inner {
    border: 1px solid #666666;
    background: #edecde;
    min-height: 100px;
    
    -moz-border-radius: 5px;
    -webkit-border-radius: 5px;
    border-radius: 5px; 
}

h1 {
    min-height: 33px;
    padding: 0 11px;
    line-height: 33px;
    font-weight: bold;
    background: -moz-linear-gradient(top, #ffd800, #ffba00);
    background: -webkit-gradient(linear,left top,left bottom, color-stop(0, #ffd800), color-stop(1, #ffba00));
    background: linear-gradient(top, #ffd800, #ffba00);
    
    filter:progid:DXImageTransform.Microsoft.Gradient(GradientType=0, StartColorStr='#ffd800', EndColorStr='#ffba00');
    position: relative;
}

h1:after {
    content: '';
    display: block;
    border-top: 10px solid #ffba00; 
    border-left: 10px solid #edecde;
    border-right: 10px solid #edecde;
    position: absolute;  
    bottom: -10px;
    left: 6px;
}

p {
    margin: 11px;   
    font-size: 14px;
}