<script language="javascript">
                 function checkForm(){
                      if(document.form1.oldpwd.value==""){
                        alert('请输入密码！');
                        return false;
                      }
                      if(document.form1.newpwd.value==""){
                        alert('请输入你的新密码！');
                        return false;
                      }
                      if(document.form1.renewpwd.value==""){
                        alert('请输入你的确认新密码！');
                        return false;
                      }                           
                       }
</script>
<%
     oldpwd =request.Form("oldpwd")
     newpwd=request.Form("newpwd")
    renewpwd=request.Form("renewpwd")
     
     set rs=server.CreateObject("adodb.recordset")
     sql="select passwd from username where username='"&session("usernaem")&"'"
     rs.open sql,conn,3,3
     if rs.eof then
     if rs("passwd")<>oldpwd then
     response.Write("<script>alert('你输入的原始密码有误，请重新输入');history.go(-1);</script>")
     response.End()
     end if
     end if
     
     if newpwd<>renewpwd then
     response.Write("<script>alert('你二次输入的新密码不一致，请重新输入');history.go(-1);</script>")
     response.End()
     end if
     conn.execute("update username set passwd ='"&newpwd&"' where username='"&session("username")&"'")     
     
     
%>
请大侠值得一下啊！

<script language="javascript">
                 function checkForm(){
                      if(document.form1.oldpwd.value==""){
                        alert('请输入密码！');
                        return false;
                      }
                      if(document.form1.newpwd.value==""){
                        alert('请输入你的新密码！');
                        return false;
                      }
                      if(document.form1.renewpwd.value==""){
                        alert('请输入你的确认新密码！');
                        return false;
                      }                           
                       }
</script>

 
上面这段JS代码要放在，输入密码的那个页面，在提交表单前验证