body {  
    font-family: Arial, sans-serif;  
    margin: 0;  
    padding: 0;  
    line-height: 1.6;  
}  
  
header, footer {  
    text-align: center;  
    padding: 1em 0;  
    background-color: #f2f2f2;  
}  
  
nav ul {  
    list-style-type: none;  
    padding: 0;  
    text-align: center;  
}  
  
nav ul li {  
    display: inline;  
    margin: 0 px;  
}  
  
nav ul li a {  
    text-decoration: none;  
    color: blue;  
}  
  
nav ul li a:hover {  
    text-decoration: underline;  
}  
  
main {  
    padding: 30px;  
}  
  
section {  
    margin-bottom: 40px;  
    border-bottom: 1px solid #ccc;  
}  
  
footer {  
    background-color: #333;  
    color: white;  
    text-align: center;  
    padding: 5px 0;  
    position: fixed;  
    width: 100%;  
    bottom: 0;  
}

table {
    width: 100%;
    border-collapse: collapse; /* 使边框合并为单一边框 */
    margin: 20px; /* 设置外边距 */
  }
 
  th, td {
    border: 1px solid black; /* 设置单元格边框 */
    padding: 8px; /* 设置内边距 */
    text-align: left; /* 设置文本对齐 */
  }
  
caption {
		font-size: 18px; /* 设置为18像素大小的字体 */
		font-weight: bold;
}