表格行列高亮显示

通过td:hover配合::before或::after，并且将其高度设置无限高，同时改变::after或::before的z-index值。

重要的一点，需要给table设置一个overflow:hidden，将伪元素溢出的高度截取掉。

  table {
     overflow: hidden;
  } 
  td, th {
    position: relative; 
    width: 40px;
    text-align: center;
  }  
  tr:hover {
    background-color: #ffa;
  }  
  td:hover::after {
    content: ""; 
    position: absolute;  
    width: 100%;  
    height: 10000px;  
    left: 0; 
    top: -5000px; 
    background-color: #ffa;  
    z-index: -1; 
  }

　　

<table cellpadding="0" cellspacing="0">
	<thead>
		<tr>
			<th></th>
			<th>1</th>
  			<th>2</th>
  			<th>3</th>
  			<th>4</th>
  			<th>5</th>
		</tr>
	</thead>
	<tbody>
		<tr>
			<td>1</td>
			<td>1-1</td>
			<td>1-2</td>
			<td>1-3</td>
			<td>1-4</td>
			<td>1-5</td>
		</tr>
		<tr>
			<td>2</td>
			<td>2-1</td>
			<td>2-2</td>
			<td>2-3</td>
			<td>2-4</td>
			<td>2-5</td>
		</tr>
		<tr>
			<td>3</td>
			<td>3-1</td>
			<td>3-2</td>
			<td>3-3</td>
			<td>3-4</td>
			<td>3-5</td>
		</tr>
		<tr>
			<td>4</td>
			<td>4-1</td>
			<td>4-2</td>
			<td>4-3</td>
			<td>4-4</td>
			<td>4-5</td>
		</tr>
		<tr>
			<td>5</td>
			<td>5-1</td>
			<td>5-2</td>
			<td>5-3</td>
			<td>5-4</td>
			<td>5-5</td>
		</tr>
	</tbody>
</table>