<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1251" />
<meta http-equiv="Pragma" content="no-cache"/>
<script type="text/javascript">
function lFilterChange()
{
var ms = document.getElementsByName('filterform')[0].getElementsByTagName('*');
alert(ms.length);
}
</script>
<title>титул</title>
</head>
<body>
<table>
<tr><td>
<FORM name="filterform">
<SELECT size="1" name="grpshow" id="grpshow" onChange="lFilterChange();">
<OPTION value="1" selected>текст1</OPTION>
<OPTION value="2">текст2</OPTION>
<OPTION value="3">текст3</OPTION>
<OPTION value="4">текст4</OPTION>
<OPTION value="5">текст5</OPTION>
<OPTION value="6">текст6</OPTION>
<OPTION value="7">текст7</OPTION>
<OPTION value="8">текст8</OPTION>
<OPTION value="9">текст9</OPTION>
<OPTION value="10">текст10</OPTION>
<OPTION value="11">текст11</OPTION>
</SELECT>
</FORM>
</td></tr></table>
</body>
</html>
Всё работает.