body {
    margin: 0;
    background-color: #f4f4f4;
    font-family: Arial, sans-serif;
    text-align: center;
}
.container {
    width: 1000px;
    margin: 0 auto; /* Canh giữa trang */
    background-color: #fff;
    box-shadow: 0 0 10px rgba(0,0,0,0.1);
}

/* Định dạng các khối ngang */
.header {
    background-color: #e6f2ff;
    height: 80px;
    line-height: 80px;
    font-size: 30px;
    font-weight: bold;
}
.banner {
    background-color: #ccffff;
    height: 100px;
    line-height: 100px;
    font-weight: bold;
}
.navigation {
    background-color: #99cccc;
    height: 40px;
    line-height: 40px;
    font-weight: bold;
}

/* Các cột phân chia bằng Float */
.sidebar-left {
    float: left;
    width: 250px;
    height: 400px;
    background-color: #a6a6a6;
    line-height: 400px;
}
.content {
    float: left;
    width: 500px;
    height: 400px;
    background-color: #cccccc;
    line-height: 400px;
}
.sidebar-right {
    float: left;
    width: 250px;
    height: 400px;
    background-color: #e6e6e6;
    line-height: 400px;
}

/* Dọn dẹp Float cho Footer */
.footer {
    clear: both;
    background-color: #f2f2f2;
    height: 60px;
    line-height: 60px;
    border-top: 1px solid #ccc;
}