Full page post-back is occurring when i m clicking on LinkButtons which are creating at runtime inside the panel1 with update panel

My aspx code is:-(LinkButton is generating in panel1 inside table)

<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>

<div align="center" >

<asp:UpdatePanel ID="Udate1" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<table width="100%" height="40px" >
<tr><td>
<asp:Label ID="lblTime" runat="server" Text="" Font-Bold="True" Font-Names="Arial"
Font-Size="X-Large" ForeColor="#e08846" />

<asp:Timer ID="timerFinish" runat="server" Interval="1000" OnTick="timerFinish_Tick">
</asp:Timer>

</td>
</tr>
</table>
</ContentTemplate>
</asp:UpdatePanel>
<asp:UpdatePanel ID="up2" runat="server">
<ContentTemplate>
<table width="100%" cellpadding="9px" cellspacing="9px" >
<tr><td width="5%" rowspan="3"></td>

<td style="border: 1px solid black" align="left" width="65%">
<table>
<tr>
<td align="left">
<u> Question: </u>
</td>

<td align="right">

<asp:Timer ID="perQuestionTime" runat="server" Interval="1000" OnTick="perQuestionTime_Tick"></asp:Timer> 

<asp:Label ID="lblperqestiontime" runat="server" Text="" Font-Bold="True" Font-Names="Arial"
Font-Size="X-Large" ForeColor="#e08846" />
</td>
</tr>
<tr>
<td colspan="2" width="70%" align="left">
<asp:Label ID="txtQuestions" CssClass="AllLabel" Width="580px" runat="server" Text="Label" Height="50px"></asp:Label><br />
<br />
<br />
<hr />
</td>
</tr>
<tr><td colspan="2" align="left"><u>Answer:</u> <br /><br /></td></tr>
<tr>
<td colspan="2" align="left">
<asp:RadioButton ID="Opt1" runat="server" GroupName="examOpt" />
<br /><br />
<asp:RadioButton ID="Opt2" runat="server" GroupName="examOpt" />
<br /><br />
<asp:RadioButton ID="Opt3" runat="server" GroupName="examOpt" />
<br /><br />
<asp:RadioButton ID="Opt4" runat="server" GroupName="examOpt" />
</td></tr>
</table>

</td>
<td valign="top" align="center" width="20%"><b>Choose Question:</b><br /> <br />
<asp:Panel ID="panel1" runat="server" BorderWidth="2px" BorderStyle="Solid" style="padding-right:10px">-------------------------------------------in this panel i m generatin linkbuttons rendomly at run time
</asp:Panel>
</td>
<td width="3%" rowspan="3"></td>
</tr>
</table>

<div align="left" >
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<asp:Button ID="btnPrev" runat="server" Text="Previous" OnClick="btnPrev_Click" CssClass="AllButton" />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<asp:Button ID="btnNext" runat="server" Text="Next" OnClick="btnNext_Click" CssClass="AllButton" />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<asp:Button ID="btnSkip" runat="server" Text="Skip" OnClick="btnSkip_Click" CssClass="AllButton" />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<asp:Button ID="btnclear" runat="server" Text="Clear Option" OnClick="btnclear_Click"
CssClass="AllButton" />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<asp:Button ID="btnFinish" runat="server" Text="Finish" OnClick="btnFinish_Click"
CssClass="AllButton" />
</div>
</ContentTemplate>
</asp:UpdatePanel>
</div>
</div>
</form>

please give suggestion me where im going wrong....