title: button inside updatepanel causes unwanted full postback
body: <p>I'm making lost password recovery on my login page and I'm doing it with ModalPopUpExtender, a Panel and two of those inside of an UpdatePanel. But somehow when clicking the "btnOkPassRequest" full postback happens. People had similiar problems with other controls, some that UpdatePanel obviously didn't encapsulate. But never with a Button. What am I missing?</p>
  
  <pre><code>&lt;asp:ScriptManager ID="ScriptManager1" runat="server"&gt;&lt;/asp:ScriptManager&gt;&lt;asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional"&gt;
  &lt;ContentTemplate&gt;  
      &lt;asp:HyperLink ID="HyperLink2" runat="server"&gt;HyperLink&lt;/asp:HyperLink&gt;
      &lt;cc1:ModalPopupExtender ID="ModalPopupExtender1" runat="server"TargetControlID="HyperLink2" BackgroundCssClass="ModalPopupBG" PopupControlID="pnlPopupPass" CancelControlID="btnCancelPassRequest" OkControlID="Button1"&gt;&lt;/cc1:ModalPopupExtender&gt;
      &lt;asp:Panel ID="pnlPopupPass" runat="server" CssClass="ModalPopup"&gt;   
        &lt;div class="ModalHeader"&gt;Password recovery&lt;/div&gt;
        &lt;div class="ModalBody"&gt;
          &lt;p&gt;Please, enter username.....&lt;/p&gt;
          &lt;table&gt;
          &lt;tr&gt;
                  &lt;td&gt;Username&lt;/td&gt;
                  &lt;td&gt;&lt;asp:TextBox ID="tbModalUserName" runat="server" class="textbox"&gt;&lt;/asp:TextBox&gt;&lt;/td&gt;            
              &lt;/tr&gt;
            &lt;/table&gt;
          &lt;table&gt;
              &lt;tr&gt;
            &lt;td&gt;&lt;/td&gt;
              &lt;td&gt;&lt;asp:Button ID="btnOKPassRequest" runat="server" Text="Request new password" CssClass="button-wide" onclick="btnOKPassRequest_Click" PostBackUrl="~/Login.aspx" /&gt;&lt;/td&gt;
              &lt;td&gt;&lt;asp:Button ID="btnCancelPassRequest" runat="server" Text="Cancel" CssClass="button-wide"/&gt;&lt;/td&gt;
              &lt;/tr&gt;
          &lt;/table&gt;        
        &lt;/div&gt;
      &lt;asp:Button ID="Button1" runat="server" Text="Button" /&gt;
      &lt;/asp:Panel&gt;
  &lt;/ContentTemplate&gt;
  &lt;Triggers&gt;
      &lt;asp:AsyncPostBackTrigger ControlID="btnOKPassRequest" EventName="btnOKPassRequest_Click" /&gt;
  &lt;/Triggers&gt;
  </code></pre>
  
  <p></p>