<ajaxToolkit:AnimationExtender ID="ae" runat="server" TargetControlID="Panel1">
 <Animations>
 <OnLoad>
 <Sequence>
 <Resize Width="1000" Unit="px" />
 <Resize Height="150" Unit="px" />
 </Sequence>
 </OnLoad>
 </Animations>
</ajaxToolkit:AnimationExtender>