经测试代码如下：
<script language="javascript">
/**
* 判断不能为空
*
* @param
* @arrange (512.笔记) jb51.cc
**/
function formcheck(){
if(document.form.zhanghao.value==""){
alert("号码不能为空！");
this.form1.zhanghao.focus();
return false;
}else if(document.form.email.value==""){
alert("内容不能为空！")
this.form1.eamil.focus();
return false;
}else form1.submit();
}
</script>
</head>
<body>
<form name="form" method="post" action="sendmail.PHP" class="formg">
<table>
<h2>
<tr>
<th colspan="8" class="CTitle">发送短信</th>
</tr>
</h2>
<body>
<tr bgcolor="#eeeeee">
<td align="center">号 码:</td>
<td><textarea name="content" cols="80" rows="15" id="zhanghao" class="formh"></textarea></td>
</tr>
<tr bgcolor="#eeeeee">
<td align="center">内 容:</td>
<td><textarea name="content" cols="80" rows="15" id="email" class="formh"></textarea></td>
</tr>
<tr bgcolor="#eeeeee" align="center">
<td height="25" colspan="2">
<input type="button" name="Submit" value="发 送" class="button" onClick="javascript：formcheck();">
<input type="reset" name="Submit2" value="重 置" class="button">
</td>
</tr>
</body>
</table>
</form>