JAVASCRIPT获取网页可见区域大小

<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>