<form id="Form1" runat="server" action="Index.aspx" method="post">
<div id="loginForm">
<table>
<tr>
<td>
</td>
<td>
<input type="hidden" value="Login" name="Login" />
</td>
</tr>
<tr>
<td>
用户名：
</td>
<td>
<input name="userName" />
</td>
</tr>
<tr>
<td>
密码：
</td>
<td>
<input id="password" name="password" />
</td>
</tr>
<tr>
<td>
<input type="submit" value="登陆" />
</td>
<td>
<input type="reset" value="取消" onclick="Reset()" />
</td>
</tr>
</table>
</div>
<div id="block">
</div>
</form>

/*登陆Form*/
#loginForm
{
border:solid 1px #AED5FD;
position:absolute;
top:35%;
left:40%;
z-index:2000;
background-color:#EAF4FE;
}
/**//*屏蔽Div*/
#block
{
background-color:#CCCCCC;
position:absolute;
top:0px;
left:0px;
z-index:1000;
display:block;
width:100%;
height:210%;
/**//*设置屏蔽div的透明度*/
filter : progid:DXImageTransform.Microsoft.Alpha ( enabled=true , style=0 , opacity=40);
}
js：
function ShowLogin()
{
var ele=document.getElementById("loginForm");
var block=document.getElementById("block");
ele.style.display="";
block.style.display="";
}
function Reset()
{
document.getElementById("loginForm").style.display="none";
document.getElementById("block").style.display="none";
}
window.onload=Reset();