javascript有效和无效时页面如何正确显示

web页面有时候无法避免使用javascript，但是如果用户浏览器不支持的话，也需要给出友好提示，以下是我作的登录页面在javascript有效和无效两种情况下的处理代码。

<noscript>您的浏览器不支持javascript，请正确设置！</noscript>
           
            <SCRIPT type="text/javascript">
            document.write('请输入用户名和密码<br><br>');           
            </SCRIPT>
            <html:form action="/Login" focus="username">
            <html:errors/>
           
            <SCRIPT type="text/javascript">
            document.writeln('<table border="0" cellpadding="5" cellspacing="5" width="320px">');
            document.writeln('<tr>');
            document.writeln('<th align="left">ID</th>');   
            document.writeln('<td align="left"><input type="text" name="username" size="30" maxlength="10"></td>');       
            document.writeln('<td></td>');       
            document.writeln('</tr>');               
            document.writeln('<tr>');       
            document.writeln('<th align="left">Password</th>');       
            document.writeln('<td align="left"><input type="password" name="password" size="30" maxlength="18"></td>');       
            document.writeln('<td></td>');
            document.writeln('</tr>');       
            document.writeln('<tr>');           
            document.writeln('<td colspan="3" align="right"><input name="login" type="image" src="/imgs/login.gif" alt="Login"></td>');       
            document.writeln('</tr>');               
            document.writeln('</table>');          
            </SCRIPT>
            </html:form>