body {
    font-family: "Times New Roman", Times, serif;
    margin: 0;
}

/* Khung ngoài */
.container {
    width: 80%;
    margin: auto;
    border: 3px solid #444;
}

/* Header */
header {
    background: #5f6b75;
    color: white;
    text-align: center;
    padding: 40px;
    font-size: 35px;
}

/* Navigation */
nav {
    float: left;
    width: 30%;
    height: 300px;
    background: #e6e6e6;
    padding: 20px;
    box-sizing: border-box;
}

nav ul {
    list-style-type: none;
    padding: 0;
}

nav ul li {
    margin-bottom: 10px;
}

/* Article */
article {
    float: left;
    width: 70%;
    height: 300px;
    padding: 20px;
    box-sizing: border-box;
    background: white;
}

/* Footer */
footer {
    clear: both;
    background: #5f6b75;
    color: white;
    text-align: center;
    padding: 15px;
}