page flickering problem on selecting a value in asp: dropdown ....

function hideList(newList, drpDwn)
{
if (drpDwn.options[drpDwn.selectedIndex].value == 'NewSearch')
{
document.getElementById(drpDwn.id).style.display="none";
document.getElementById(newList.id).style.display="inline";
return false;
}
else
{
return true;
}
}
function hideTable(newList, drpDwn)
{
document.getElementById(newList).style.display="none";
document.getElementById(drpDwn).style.display="inline";
document.getElementById(drpDwn).selectedIndex=0;
}


some design page code
------------------------------
<asp: DropDownList ID="drpMoveItemsTo" runat="server" OnSelectedIndexChanged="drpMoveItemsTo_SelectedIndexChanged"
Width="150px" AutoPostBack="True">
</asp: DropDownList></td>
</tr>
<tr>
<td style="width: 126px">
<table id="newListName" style="width: 151px">
<tr>
<td style="width: 64px; height: 26px;">
<asp:TextBox ID="txtNewListName" runat="server" Width="61px"></asp:TextBox></td>
<td style="width: 30px; height: 26px;">
<asp:LinkButton ID="lnkAddList" runat="server" Font-Names="Arial" Font-Size="X-Small"
Font-Underline="True" ForeColor="Blue" OnClick="lnkAddList_Click">Add</asp:LinkButton></td>
<td style="font-size: 9pt; height: 26px">
<a id="lnkCancelNewList" href=" hideTable('newListName', '<%=drpMoveItemsTo.ClientID %>')"
style="font-size: 12px; font-family: Arial"><span style="color: #000000">Cancel</span></a>
</td>
</tr>
</table>

NOW THE PROBLEM IS
******************************************************

asp: dropdown autopostback set to true ...

When i select a particular value in asp: dropdown it will call a javascript function[above said, hideList(newList, drpDwn)] and hide the dropdown and show a table and last line of code says, return false. It means, not to postback, that means "NO FLICKERING OF PAGE". But here the page get flickered but i check it is not going back to page_load, that means, no postback. But still the page get flickered.

Now on hiding the asp: dropdown, a table with three controls will be shown and on click of a link in that table, the table will get hided and dropdown will displayed back. javascript function above shown [hideTable(newList, drpDwn)]. But here, there is no flickering happens. It will hide the table with controls and shows the dropdown, but no page flickering ... works fine ..

So why it is happening the page flicker on asp: dropdown onchange event even after returning false ......... any fix ?

Hope the question is clear .......