我有一段php的代码，麻烦能帮我写一下注释吗，尤其是html部分，感觉看不懂呀

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>人事管理系统-用户登录</title>
<style type="text/css">
<!--
*{overflow:hidden; font-size:9pt;}
body {
margin-left: 0px;
margin-top: 0px;
margin-right: 0px;
margin-bottom: 0px;
background-image: url(images/bg.gif);
background-repeat: repeat-x;
}
.STYLE2 {
color: #990000;
font-size: 14pt;
font-family: "楷体_GB2312";
font-weight: bold;
}
-->
</style>
<script language="javascript" type="text/javascript">
function CheckForm()
{
if (document.login.user_no.value.length == 0) {
alert("请输入用户名称!");
document.login.user_no.focus();
return false;
}
if (document.login.user_pass.value == "") {
alert("请输入密码!");
document.login.user_pass.focus();
return false;
}
return true;
}
</script></head><body>
<table width="100%"  height="100%" border="0" cellspacing="0" cellpadding="0">
  <tr>
    <td><table width="100%" border="0" cellspacing="0" cellpadding="0">
      <tr>
        <td height="561" style="background:url(images/lbg.gif)"><table width="940" border="0" align="center" cellpadding="0" cellspacing="0">
          <tr>
            <td height="238" style="background:url(images/login01.jpg)">&nbsp;</td>
          </tr>
          <tr>
            <td height="190"><table width="100%" border="0" cellspacing="0" cellpadding="0">
              <tr>
                <td width="208" height="190" style="background:url(images/login02.jpg)">&nbsp;</td>
                <td width="518" style="background:url(images/login03.jpg)">
<form action="CheckLogin.php" method="post" name="login" id="login" onSubmit="return CheckForm();">
                  <table width="389" border="0" align="center" cellpadding="0" cellspacing="0">
                    <tr>
                      <td width="40"><img src="images/user.gif" width="30" height="30"></td>
                      <td width="54" height="40">用户:</td>
                      <td width="295"><input type="text" name="user_no" id="user_no" style="width:164px; height:32px; line-height:34px; background:url(images/inputbg.gif) repeat-x; border:solid 1px #d1d1d1; font-size:9pt; font-family:Verdana, Geneva, sans-serif;"></td>
                    </tr>
                    <tr>
                      <td><img src="images/password.gif" width="28" height="32"></td>
                      <td height="40">密码:</td>
                      <td><input type="password" name="user_pass" id="user_pass" style="width:164px; height:32px; line-height:34px; background:url(images/inputbg.gif) repeat-x; border:solid 1px #d1d1d1; font-size:9pt; "></td>
                    </tr>
 <tr>
                      <td><img src="images/user.gif" width="30" height="30"></td>
                      <td height="40">用户类型</td>
                      <td><label>
                        <input type="radio" name="identify" value="admin" checked>
                        系统管理员
                        <input name="identify" type="radio" value="yg">
                       员工
                        </td>
                    </tr>                    <tr>
                      <td>&nbsp;</td>
                      <td height="40" colspan="2">
                        <div align="left">                            <input type="image" border="0" name="imageField" src="images/login.gif" width="95" height="34" onClick="javascript:Login.submit();" alt="登录系统" >
                          <a href="manager/user.asp"></a> </div></td>
                      </tr>
                  </table>
                        </form>
                </td>
                <td width="214" style="background:url(images/login04.jpg)" >&nbsp;</td>
              </tr>
            </table></td>
          </tr>
          <tr>
            <td height="133" style="background:url(images/login05.jpg)"><br>
            <div align="center" class="STYLE2">copyright&copy;<?php echo date("Y")?>  </div></td>
          </tr>
        </table></td>
      </tr>
    </table></td>
  </tr>
</table>
</body>
</html>
代码