asp.net给页面增加一个层

在做登录的时候想着别老是用跳转页面，用户体验超差的，而且对于网速慢的用访来说，还要去跳转一次重新加载一个新的页面，显得有点不爽！就弄了一个层直接在当前页面跳转！

废话不说直接上代码！

function ShowNo() //隐藏两个层 
{
    document.getElementById("doing").style.display = "none";
    document.getElementById("divLogin").style.display = "none";
}
function $(id) {
    return (document.getElementById) ? document.getElementById(id) : document.all[id];
}
function showFloat() //根据屏幕的大小显示两个层 
{
    var range = getRange();
    $('doing').style.width = range.width + "px";
    $('doing').style.height = range.height + "px";
    $('doing').style.display = "block";
    document.getElementById("divLogin").style.display = "";
}
function getRange() //得到屏幕的大小 
{
    var top = document.body.scrollTop;
    var left = document.body.scrollLeft;
    var height = document.body.clientHeight;
    var width = document.body.clientWidth;

    if (top == 0 && left == 0 && height == 0 && width == 0) {
        top = document.documentElement.scrollTop;
        left = document.documentElement.scrollLeft;
        height = document.documentElement.clientHeight;
        width = document.documentElement.clientWidth;
    }
    return { top: top, left: left, height: height, width: width };
} 
<a href="javascript:void(0)" onclick="showFloat()">新增</a> 
            <!--加一个半透明层-->
            <div id="doing" style="filter: alpha(opacity=30); -moz-opacity: 0.3; opacity: 0.3;
                background-color: #000; width: 100%; height: 100%; z-index: 700; position: absolute;
                left: 0; top: 0; display: none; overflow: hidden;">
            </div>
            <!--加一个登录层-->
            <div id="divLogin" style="border: solid 10px #898989; background: #fff; padding: 10px;
                width: 780px; z-index: 701; position: absolute; display: none; top: 50%; left: 50%;
                margin: -200px 0 0 -400px;">
                <div style="padding: 3px 15px 3px 15px; text-align: left; vertical-align: middle;">
                    <div>
                        用户：
                        <asp:TextBox ID="TxtUserName" runat="server"> </asp:TextBox>
                    </div>
                    <div>
                        密码：
                        <asp:TextBox ID="TxtUserPwd" runat="server" TextMode="Password"> </asp:TextBox>
                    </div>
                    <br />
                    <div>
                        &nbsp; &nbsp;
                        <asp:Button ID="BttLogin" runat="server" Text=" 登 陆 " />&nbsp;
                        <input id="BttCancel" type="button" value=" 取 消 " onclick="ShowNo()" />
                    </div>
                </div>
            </div>
            <br />
        </div>