Get error when accessing RadioButtonList from javascript that exist in a page that have master page
<p>i have a asp.net page that have its master page and it contain RadioButtonList1 and i try to do thefollwing </p>

<pre><code>&lt;script type="text/javascript"&gt;


            var radioButtonList = document.getElementById('&lt;%=RadioButtonList1.ClientID%&gt;');
            if(radioButtonList[0].checked)
                document.getElementById("_secondTR").style.display = "block";
            else if (radioButtonList[1].checked )
                document.getElementById("_secondTR").style.display = "none";
        }  
&lt;/script&gt;

&lt;table style="width: 100%"&gt;
    &lt;tr id="Tr1"&gt;
        &lt;td&gt;
            &lt;asp:RadioButtonList ID="RadioButtonList1" runat="server"  BackColor="#FFCC99"
                RepeatDirection="Horizontal" Width="117px" onclick="ShowHide()"&gt;
                &lt;asp:ListItem Value="1"&gt;Yes&lt;/asp:ListItem&gt;
                &lt;asp:ListItem Value="0"&gt;No&lt;/asp:ListItem&gt;
            &lt;/asp:RadioButtonList&gt;
        &lt;/td&gt;
    &lt;/tr&gt;
    &lt;tr id="_secondTR" runat="server" style="display: none"&gt;
        &lt;td&gt;
            &lt;asp:RadioButton ID="Five" runat="server" GroupName="1" BackColor="#669999" /&gt;
            &lt;asp:RadioButton ID="Four" runat="server" GroupName="1" CausesValidation="True" BackColor="#669999" /&gt;
        &lt;/td&gt;
    &lt;/tr&gt;
&lt;/table&gt;
</code></pre>

<p>i can't get RadioButtonList1 from java script ... could any help me to get that ? </p>
