#tb, tb1, tr, th, td {
border: 5px solid blue;
/*加边框*/
padding: 5px;
/*内边距*/
}
#tb1 {
border-collapse: collapse;
/*合并边框*/
width: 500px;
height: 500px;
text-align: center;
background-color: aqua;
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>表格及轮廓</title>
<link rel="stylesheet" href="tzy.css" type="text/css">
</head>
<body>
<table id="tb">
<tr class="alt">
<th>姓名</th>
<th>年龄</th>
<th>性别</th>
</tr>
<tr>
<td>小王</td>
<td>15</td>
<td>男</td>
</tr>
<tr class="alt">
<td>小王</td>
<td>15</td>
<td>男</td>
</tr>
<tr>
<td>小王</td>
<td>15</td>
<td>男</td>
</tr>
</table>
<br/>
<table id="tb1">
<tr>
<th>姓名</th>
<th>年龄</th>
<th>性别</th>
</tr>
<tr>
<td>小王</td>
<td>15</td>
<td>男</td>
</tr>
<tr>
<td>小王</td>
<td>15</td>
<td>男</td>
</tr>
<tr>
<td>小王</td>
<td>15</td>
<td>男</td>
</tr>
</table>
<br/>
<br/>
<p style="outline-style: groove;outline-width: 1px">文字效果实心框</p>
<br/>
<br/>
<p style="outline-style: double;outline-width: 20px">文字效果双虚线框</p>
</body>
</html>