When you have a panel with a style of absolute, and set the panel visible to false, the div tags are left, leaving a blank line on your page. This only happens if your using AjaxManager.
Per the visible tag, the control shouldn't be rendered at all.
This is a major issue with the way we have our application structured, as we use allot of overlays (absolute positioned) panels.
Sample aspx
<
telerik:RadScriptManager ID="RadScriptManager1" runat="server">
</telerik:RadScriptManager>
<telerik:RadAjaxManager ID="RadAjaxManager1" runat="server">
<AjaxSettings>
<telerik:AjaxSetting AjaxControlID="btnShow">
<UpdatedControls>
<telerik:AjaxUpdatedControl ControlID="PanelTest" />
</UpdatedControls>
</telerik:AjaxSetting>
<telerik:AjaxSetting AjaxControlID="btnHide">
<UpdatedControls>
<telerik:AjaxUpdatedControl ControlID="PanelTest" />
</UpdatedControls>
</telerik:AjaxSetting>
</AjaxSettings>
</telerik:RadAjaxManager>
<asp:Button ID="btnShow" runat="server" Text="Show Panel" />
<asp:Button ID="btnHide" runat="server" Text="Hide Panel"/>
<br />
Just before the Panel
<
asp:Panel ID="PanelTest" runat="server" style="position:absolute; background-color: WhiteSmoke;border-color:LightGrey;border-width:3px;border-style:Ridge;" Visible="true">
This is a test area that is to be shown absolute positioned
</asp:Panel>
Just After the Panel
CodeBehind
Protected
Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not IsPostBack Then
Me.PanelTest.Visible = False
End If
End Sub
Private Sub btnShow_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnShow.Click
Me.PanelTest.Visible = True
End Sub
Private Sub btnHide_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnHide.Click
Me.PanelTest.Visible = False
End Sub