如何垂直對齊此超鏈接按鈕？

Question

我想垂直居中這些超鏈接。但是，我無法弄清楚我在我的css代碼中遺漏了什麼。我錯過了什麼？

 <tr> 
     <td id="nav"><a href="demopage.html">1</a></td> 
     <td id="nav"><a href="demopage.html">2</a></td> 
     <td id="nav"><a href="demopage.html">3</a></td> 
    </tr> 
    <tr style="height: 45px"> 
     <td id="nav"><a href="demopage.html">4</a></td> 
     <td id="nav"><a href="demopage.html">5</a></td> 
     <td id="nav"><a href="demopage.html">6</a></td> 
    </tr> 

CSS代碼：

#nav a { 
text-decoration:none; 
display:block; 
background-color:#99ccff; 
border: 1px solid #000000; 
list-style-type: none; margin:0; padding:0; 
width: 125px; 
height: 25px; 
text-align:center; 
vertical-align:middle; 
margin-top: auto  
     } 
#nav a:link { 
color:black; 
    } 
    #nav a:visited { 
color:#000000; 
} 

#nav a:hover { 
color:#000000; 
background-color:#EAEAEA; 
} 

Answer 1

給的鏈接線高度母公司相同的高度：JS Fiddle

#nav a { 
    text-decoration:none; 
    display:block; 
    background-color:#99ccff; 
    border: 1px solid #000000; 
    list-style-type: none; 
    margin:0; 
    padding:0; 
    width: 125px; 
    height: 25px; 
    text-align: center; 
    line-height: 25px; 
    margin-top: auto 
}