Not able to Create ActiveXObject via javascript

I am trying to trigger an email from my lotus notes using javascript. When I am trying to run the code as a .html file from my system. Its working absolutely fine. But when I include the same code in an application and try to run the same using http://localhost:portno , I am getting error that "ActivexObject cannot be resolved to a type".

The script is as given below:

 <script language="javascript" type="text/javascript">
function SendScriptMail() {
    var mToMail = document.getElementById('txtMailId').value
    var mSub = document.getElementById('txtSubject').value
    var mMsg = document.getElementById('txtContent').value
 
    var Session;
    var Maildb;
    var UI;
    var MailDoc;
    try {
        // Create the Activex object for NotesSession
        var Session = new ActiveXObject('Notes.NotesSession');
  //alert(mMsg);
  //alert(Session);
        if (Session == null) {
            throw("NoSession");
        } else {
            // Get mail database
   //var UserName  = Session.UserName;
   //MailDbName = UserName.substring(0,1) + UerName.substring(UserName.indexOf( " " ,1) + 1 ,UserName.length) + ".nsf"
            Maildb = Session.GetDatabase("", "");
   //alert("VCA10177.nsf" + UserName);
            Maildb.OPENMAIL();
   
            if (Maildb == null) {
                throw("NoMaildb");
            } else {
                // Create the ActiveX object for NotesUIWorkspace
                UI = new ActiveXObject('Notes.NotesUIWorkspace');
                if (UI == null) {
                    throw("NoUI");
                } else {
    //alert("jj");
                    MailDoc=UI.Composedocument(Maildb.SERVER, Maildb.FILEPATH, 'Memo');
     //alert(Maildb.SERVER);
                    if (MailDoc == null) {
                        throw('NoMailDoc');
                    } else {
                        // Populate the fields
                        MailDoc.Fieldsettext('SendTo', mToMail);
                        MailDoc.Fieldsettext('Subject', mSub);
                        // insert message body and place cursor at end of text
                        MailDoc.Gotofield('Body');
                        MailDoc.Inserttext(mMsg);
                        // destroy the objects
                        Session.Close();
                        Session = null;
                        UI = null;
                        Maildb = null;
                        MailDoc = null;
                    }
                }
            }
        }
    } catch (err) {
        // feel free to improve error handling...
        alert('Error while sending mail');
    }
}
    </script>