<script language="javascript" type="text/javascript">
    function getClientBounds()
    {
        var clientWidth;
        var clientHeight;
        
        if ($.browser.msie)
        {
            clientWidth = document.body.clientWidth;
            clientHeight = document.body.clientHeight;
        }
        else if ($.browser.safari)
        {
            clientWidth = window.innerWidth;
            clientHeight = window.innerHeight;
        }
        else if ($.browser.opera)
        {
            clientWidth = Math.min(window.innerWidth,
                document.body.clientWidth);
            clientHeight = Math.min(window.innerHeight,
                document.body.clientHeight);
        }
        else
        {
            clientWidth = Math.min(window.innerWidth,
                document.documentElement.clientWidth);
            clientHeight = Math.min(window.innerHeight,
                document.documentElement.clientHeight);
        }
 
        return { width : clientWidth, height : clientHeight };
    }
 
    function resetLiveMessengerPosition()
    {
        var clientBounds = getClientBounds();
        var container = document.getElementById("liveMessengerContainer");
        
        var scrollLeft = (document.documentElement.scrollLeft ?
            document.documentElement.scrollLeft : document.body.scrollLeft);
        var scrollTop = (document.documentElement.scrollTop ?
            document.documentElement.scrollTop : document.body.scrollTop);
                
        var containerLeft = scrollLeft + clientBounds.width - 
            container.clientWidth – 5;
        var containerTop = scrollTop + clientBounds.height - 
            container.clientHeight;
                
        $("#liveMessengerContainer").css(
            {top : containerTop + "px", left : containerLeft + "px"});
    }
<script>

<div id="liveMessengerContainer" style="position:absolute;">
    <div style="border: solid 1px black; width:160;
         height: 39px; cursor:pointer;
         background-image:url(Messenger_Header_bg.gif)"
         id="liveMessengerThumb">
        <img src="Messenger_logo_beta.gif"
             alt="使用Live Messenger联系我"
             style="margin: 10px 10px 0px 9px;"/>
    </div>
    <table border="0" cellpadding="0" cellspacing="0"
           id="liveMessengerPanel">
        <tr>
            <td valign="top">
                <img id="hideLiveMessengerPanel"
                     style="cursor:pointer; margin-right: 3px;"
                     src="Messenger_close_sm.gif" alt="关闭" />
            </td>
            <td>
                <iframe
                    src="..." width="300" frameborder="0"
                    style="border: solid 1px black; width: 300px;
                    height: 400px;"></iframe>
            </td>
        </tr>
    </table>
<div>

<script language="javascript" type="text/javascript">
    $("#liveMessengerPanel").hide();
    
    $(document).ready(function(){
        $(window).scroll(resetLiveMessengerPosition);
        $(window).resize(resetLiveMessengerPosition);
    
        resetLiveMessengerPosition();
        
        $("#liveMessengerThumb").click(function(){
            $("#liveMessengerThumb").fadeOut(500, function(){
                $("#liveMessengerPanel").fadeIn(500, function(){
                    resetLiveMessengerPosition();
                });
                resetLiveMessengerPosition();
            });
        });
        
        $("#hideLiveMessengerPanel").click(function(){
            $("#liveMessengerPanel").fadeOut(500, function(){
                $("#liveMessengerThumb").fadeIn(500, function(){
                    resetLiveMessengerPosition();
                });
                resetLiveMessengerPosition();
            });
        });
    });
<script>