<script type="text/javascript">
var oFileChecker = document.getElementById("fileChecker");

function changeSrc(filePicker)
{
    oFileChecker.src = filePicker.value;
}

oFileChecker.onreadystatechange = function ()
{
    if (oFileChecker.readyState == "complete")
    {
        checkSize();
    }
}

function checkSize()
{
    var limit  = document.getElementById("fileSizeLimit").value * 1024;

    if (oFileChecker.fileSize > limit)
    {
        alert("too large");
    }
    else
    {
        alert("ok");
    }
}
</script>  

 <embed id="fileChecker" src="playswf.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash"></embed>
<script type="text/javascript">
var oFileChecker = document.getElementById("fileChecker");

function changeSrc()
{
    oFileChecker.src = "http://www.jkjk.com/swf/actionscript.swf";
}

oFileChecker.onreadystatechange = function ()
{
    if (oFileChecker.readyState == "complete")
    {
        checkSize();
    }
}

function checkSize()
{
    var limit  = document.getElementById("fileSizeLimit").value * 1024;

    if (oFileChecker.fileSize > limit)
    {
        alert("too large");
    }
    else
    {
        alert(oFileChecker.fileSize);
    }
}
changeSrc()
</script>