hi dmytry.kiev, i had the same problem as you when the gridview until i bound it and set the datasource and so on. works fine now. Put it under <Content>
<ajaxToolkit:AccordionPane ID="AccordionPane2" runat="server" ToolTip="Click this" CssClass="panecss">
<Header>
<img src="images/Inbox.gif" height="10" width="10" /> <asp:LinkButton ID="LinkButton2" runat="server" CssClass="selectedbutton">second</asp:LinkButton>
</Header>
<Content>
<asp:LinkButton ID="LinkButton3" runat="server">two-1</asp:LinkButton><br />
<asp:LinkButton ID="LinkButton4" runat="server">two-2</asp:LinkButton><br />
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="LP"
DataSourceID="SqlDataSource1">
<Columns>
<asp:BoundField DataField="LP" HeaderText="LP" ReadOnly="True"
SortExpression="LP" />
<asp:BoundField DataField="Year" HeaderText="Year" SortExpression="Year" />
<asp:BoundField DataField="Info" HeaderText="Info" SortExpression="Info" />
<asp:BoundField DataField="GroupName" HeaderText="GroupName" SortExpression="GroupName" />
<asp:BoundField DataField="Name" HeaderText="Name" SortExpression="Name" />
</Columns>
</asp:GridView>
</Content>
</ajaxToolkit:AccordionPane>
awni