document.frmRing.submit()问题

执行document.frmRing.submit()
提示错误:对象不支持该属性或方法
页面代码
<%@ Page language="c#" Codebehind="testInputRingInfo.aspx.cs" AutoEventWireup="false" Inherits="testXuanLing.testInputRingInfo" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" > <html>
  <head>
    <title>testInputRingInfo</title>
    <meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
    <meta name="CODE_LANGUAGE" Content="C#">
    <meta name=vs_defaultClientScript content="JavaScript">
    <meta name=vs_targetSchema content="http://schemas.microsoft.com/intellisense/ie5">
    <script language ="javascript">
function submitRingInfo()
{
document.frm.submit();
}
    </script>
  </head>
  <body>

    <form name="frm" method="post" action="uploadRing.aspx" enctype="multipart/form-data">
      <table width="800" height="400" border="0" cellpadding="0">
        <tr>
          <td width="105">铃音编号：</td>
          <td width="596"><input name="ringId" type="text"></td>
          <td width="91">&nbsp;</td>
        </tr>
        
        <tr>
          <td colspan="3"><div align="center">
            <input type="button" name="submit" value="上传" onclick="submitRingInfo()">
            <input type="button" name="cancel" value="取消">
          </div></td>
        </tr>
      </table>
  </form>

  </body>
</html>