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                        /CSS Sprite雪碧圖應用

求助為什么我不能編輯那兩個button

<!DOCTYPE?html?PUBLIC?"-//W3C//DTD?XHTML?1.0?Transitional//EN"?"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html?xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta?http-equiv="Content-Type"?content="text/html;?charset=utf-8"?/>
<title>無標題文檔</title>
<style>
????*{margin:0;padding:0;}
???
????.container{
???????
????????width:220px;
????????height:350px;
????????background:#ebf2fa;
????
????}
????.form_m{
????????padding:15px;
????????
????}
????.input_text{
????????
????????display:block;
????????width:180px;
????????height:28px;
????????margin-top:12px;
????????border-radius:4px;/*圓角矩形*/
????????text-indent:20px;/*文字縮進，需塊元素或內聯塊元素*/
??????
????}
????
????
????p{
????????margin-top:10px;
????????height:50px;
????????font-size:13px;
????}
????p?label{
????????
????????vertical-align:?top;
???????????
????}
????p?a{
???????
????????text-decoration:none;
????????float:right;
????????
????}

????}
????.btn{
????width:200px;
????height:20px;
????background:url(http://img1.sycdn.imooc.com//539a972b00013e9102280177.jpg)
????}
????
</style>
</head>

<body>
<div?class="container">
????<form?class="form_m">
????????<input?class="input_text"?placeholder="郵箱/手機號/用戶名"?type="text"/>
????????<input?class="input_text"?placeholder?="請輸入密碼"type="password"/>
????????<p>
????????????<input?class="checkbox"?type="checkbox"?id="1"/>
????????????<label?for="1">下次自動登陸</label>
????????????<a?href="javascript:;">忘記密碼?</a>
????????</p>
????????<input??class="btn"?type="submit"?value="登陸"/>
????????<hr/>?
????????<input?class="btn"?type="button"?value="注冊"/>
????</form>
</div>

</body>
</html>

怎么改都沒用