这个是javascript里面的知识，搞不出来。。。伤脑筋啊 - 黑马程序员技术交流社区

<P><head>
<title>表单注册</title>
<style type="text/css">
table{
border:#0066ff 1px solid;
width:500px;
border-collapse:collapse;
}
table td,table th{
padding:2px;
}
.errorinfo{
color:#ff0000;
display:none;
}
</style>
<script type="text/javascript">
//校验性别是否填写
function checkSex(){
var temp=false;
var xbObj1=document.getElementById("nan");
var xbObj2=document.getElementById("nv");
if(xbObj1.checked || xbObj2.checked){
temp=true;
}
return temp;
}
function checkform(sexNode){
var divNode=document.getElementById("sexdiv");
if(!checkSex()){
sexNode.className="error";
divNode.style.display="block";
return false;
}
else{
sexNode.className="norm";
divNode.style.display="none";
}
}
</script>
</head>
<body>
<form>
<table>
<tr>
<th>注册表单</th>
</tr></P>
<P>
tr>
<th>
<div>
性别:<input type="radio" name="sex" id="nan" onblur="checkform(this)"/>男
<input type="radio" name="sex" id="nv" onblur="checkform(this)"/>女
</div>
<div class="errorinfo" id="sexdiv">必填</div>
</th>
</tr></P>
<P>
<tr>
<th>
<div>
城市:<select name="country" onblur="checkCounty(this)">
<option value="none">--选择省份--</option>
<option value="hainan">海南省</option>
<option value="guangdong">广东省</option>
<option value="hunan">湖南省</option>
<option value="other">其他</option>
</select>
</div>
<div class="errorinfo" id="countydiv">必填</div>
</th>
</tr>
<tr>
<th>
<div>兴趣爱好</div>
<div><input type="checkbox" name="interests" value="basketball"/>篮球
<input type="checkbox" name="interests" value="football"/>足球
<input type="checkbox" name="interests" value="music"/>音乐
<input type="checkbox" name="interests" value="film"/>电影
<input type="checkbox" name="interests" value="others"/>其他</div>
<div class="errorinfo" id="interestsdiv">必填</div>
</th>
</tr>
</table>
</form>
</body></P>

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