JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8" />
        <title>Градиент</title>
        <style>
            body {
                background:url(http://htmlbook.ru/example/images/redline.png);
                font-family:tahoma;
            }
            
            #ourblock {
                min-height:100px;                
                border-radius:5px;
                background: #5ca595; 
                background:-moz-linear-gradient(100% 100% 90deg, #5ca595, #61ccb4);
                background:-webkit-gradient(linear, left top, left bottom, from(#61ccb4), to(#5ca595));
                background:-o-linear-gradient(#61ccb4, #5ca595);
                opacity:0.6;
                position:relative;
                width:100%;
                z-index: -1;
            }
            
            #container {
                margin-top:-100px;
                border-radius:5px;
                border:2px solid #004c3b;
                min-height:84px;
                box-sizing: content-box;
                padding:6px;
            }
            
            #main {
                border:1px solid #000;
                border-radius:4px;
                overflow:hidden;
            }
            
            #header {
                background: #fed800; 
                background:-moz-linear-gradient(100% 100% 90deg, #ffba00, #fed800);
                background:-webkit-gradient(linear, left top, left bottom, from(#fed800), to(#ffba00));
                background:-o-linear-gradient(#fed800, #ffba00);
                font-size:15px;                
                padding:6px 8px;
                border-radius:4px 4px 0 0;
            }
            
            #content {
                background:#fff;
                padding:8px;
                font-size:12px;
                height:36px;
                border-radius:0 0 4px 4px;
            }
        </style>
    </head>
    <body>
        <div id="ourblock"></div>
       ...