I want change the color of the panel if i click checkbox using javascript

[itsenthil]

This is my UserControl(ascx) coding, it is not working plz help me to rectify the error.....what is wrong in that one.....

<%@ Control Language="vb" AutoEventWireup="false" Codebehind="Usea.ascx.vb" Inherits="HIS.Usea" TargetSchema="http://schemas.microsoft.com/intellisense/ie5" %>
<script language="javascript" type="text/javascript">
function output()
{
var xx = document.getElementsByName("cbtest").value;
// var xx=document.forms.item('cbtest');
//document.m
//var xx= document.forms.cbtest.checked= true;
// var mainForm=document.mainForm.cbtest;
if (xx.checked ==true)
{
document.getElementById("Panel1").style.background Color= "#ffff00";
return true;
}
if(xx.checked == false)
{
document.getElementById("Panel1").style.background Color= "#90dd90";
return false;
}
}
</script>
<asp:panel id="Panel1" BackColor="YellowGreen" runat="server" Width="56px" Height="40px" BorderStyle="None"
ToolTip="seat">
<asp:Image id="Image1" runat="server" Width="32px" Height="32px" ImageAlign="Middle" ImageUrl="file:///\\system107\HIS\Images\seat2.jpg"></asp:Image>
<INPUT id="cbtest" onclick="output()" type="checkbox" name="cbtest" runat="server">
<asp:Label id="Label1" runat="server" Width="32px" Font-Size="X-Small" Font-Names="Verdana"></asp:Label>
</asp:panel>

[kenobewan]

What error are you getting?

[itsenthil]

What error are you getting?

'Checked' is null or not an object