经测试代码如下：
<script language=javascript>
/**
* 判断不能为空
*
* @param
* @arrange (编程之家) 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>
