Can't Load external XML document? Can't load external css document?

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
    <title></title>
    <meta content="text/html; charset=utf-8" http-equiv="Content-Type" />
    <style type="text/css">
        BODY
        {
            background-color: #000000;
            margin: 0px;
        }
    </style>    <script type="text/javascript" src="common.js"></script>    <meta name="GENERATOR" content="MSHTML 8.00.6001.18241" />
</head>
<body>
    <table border="0" cellspacing="0" cellpadding="0" width="100%" height="100%">
        <tbody>
            <tr>
                <td align="middle">                    <script language="JavaScript" type="text/javascript">
<!--
                        appOnLoad();                        function launchPopup(cultureID, officeID, currentSkill, indexPos, lang, rtl, domain) {                            w = 290;
                            h = 470;
                            l = screen.availWidth - w - 20;
                            t = 10;
                            var url = "xx00";                             PopupWin = window.open(url, "PopupWin", "top=" + t + ",left=" + l + ",width=" + w + ",height=" + h + ",resizeable=0,menubars=0,toolbars=0,scrollbars=0,status=0");                            PopupWin.focus();
                            self.moveTo(10, screen.availHeight + 100);
                        }

                        function openHome() {
                            eraseCookie("officeID");

                            //var url = "";

//To support language folder
var cultureId =QueryString("cultureID");
                            var url = cultureId+'/index.htm?';                            if (QueryString("skillID") != "") {
                                url += "skillID=" + QueryString("skillID") + "&";
                            }                            if (QueryString("showgroup") == "true") {
                                url += "showgroup=true";
                            }                        
                        writeFlash("HelpGuide_Web.swf", "mainGUI", 900, 635, "app.htm");
//-->
                    </script>                </td>
            </tr>
        </tbody>
    </table>
</body>
</html>
html源代码, 用网页打开的时候, 会出现下面的错误:Can't Load external XML document? 
Can't load external css document?是什么原因呢?