Develop Reference

10% margin on popup

how can i make this modal popup fill 80% of the screen in the x and y direction. i.e a margin of 10% on each side
Markup
<!-- Add Files Modal Form -->
<asp:HiddenField ID="AddFilesForModal" runat="server" />
<ajaxToolkit:ModalPopupExtender runat="server" ID="AddFilesModal" BehaviorID="modalPopupExtenderAddFiles"
TargetControlID="dummyButtonAddToPendingList" PopupDragHandleControlID="PanelAddFilesOuter" PopupControlID="PanelAddFilesOuter"
OkControlID="dummyButtonAddToPendingList" BackgroundCssClass="ModalTreeviewBackgroundz" DropShadow="false"
Drag="true">
</ajaxToolkit:ModalPopupExtender>
<ajaxToolkit:RoundedCornersExtender ID="RoundedCornersExtender4" runat="server" TargetControlID="PanelAddFilesInner">
</ajaxToolkit:RoundedCornersExtender>
<asp:Panel ID="PanelAddFilesOuter" runat="server" BackColor="Transparent" Style="display: none;">
<asp:Panel ID="PanelAddFilesInner" runat="server" BackColor="White" >
<ContentTemplate>
<div id="AddFilesContainer">
<br />
<div style="max-height:800px;overflow:auto;">
<asp:TreeView ID="TreeViewAddItems" runat="server" BorderStyle="Solid" ShowCheckBoxes="Leaf"
Width="99%" ImageSet="XPFileExplorer" NodeIndent="15" PathSeparator="\" ShowExpandCollapse="true"
EnableClientScript="true" OnTreeNodeCheckChanged="OnTreeNodeCheckChanged" OnAdaptedTreeNodeCheckChanged="OnTreeNodeCheckChanged" ShowLines="True">
<HoverNodeStyle Font-Underline="True" ForeColor="#6666AA" />
<NodeStyle Font-Names="Tahoma" Font-Size="8pt" ForeColor="Black" HorizontalPadding="2px"
NodeSpacing="0px" VerticalPadding="2px" />
<ParentNodeStyle Font-Bold="False" />
<SelectedNodeStyle BackColor="#B5B5B5" Font-Underline="False" HorizontalPadding="0px"
VerticalPadding="0px" />
</asp:TreeView>
</div>
<br />
<div class="base">
<asp:LinkButton ID="lnkAddToPendingList" runat="server" OnClick="BtnAddToPendingList_Click" BorderStyle="Solid" BackColor="#CCCCCC">Add selected items to list</asp:LinkButton>
<asp:Button CssClass="Button" ID="dummyButtonAddToPendingList" runat="server" Style="display: none;" />
<asp:Button CssClass="Button" ID="CancelAddFiles" runat="server" Text="Cancel" OnClientClick="$find('modalPopupExtenderAddFiles').hide(); return false;" />
</div>
</div>
</ContentTemplate>
</asp:Panel>
</asp:Panel>
<!-- End Add Files Modal Form -->

Look at the resulting HTML, and style it with CSS. The CSS likely will look something like this:
.modal {
display: block;
width: 90%;
height: 90%;
margin: auto;
}

How to make ModalPopup drag/drop

I use a ModalPopupExtender from the Ajax ControlToolkit in my Webapplication.I set it's Drag property is true,but when I drag the popup panel and drop it at the new position,it comes back the original position at once.I want to get the effect like the Sample, can drag/drop at different position. How in the example on the page ..
http://www.asp.net/ajaxLibrary/AjaxControlToolkitSampleSite/ModalPopup/ModalPopup.aspx
Here My Code:
<form id="form1" runat="server">
<asp:scriptmanager id="ScriptManager1" runat="server">
</asp:scriptmanager>
<asp:button id="btnAddNew" runat="server" text="New Expanse" />
<asp:modalpopupextender id="ModalPopupExtender1"
runat="server" cancelcontrolid="btnCancel"
okcontrolid="btnOkay" targetcontrolid="btnAddNew"
popupcontrolid="Panel1" popupdraghandlecontrolid="PopupHeader"
drag="true" backgroundcssclass="ModalPopupBG">
</asp:modalpopupextender>
<div class="popupConfirmation" id="Panel1" style="display: none">
<iframe id="frameeditexpanse" src="Benutzer.aspx" frameborder="1" height="500px" width="520px">
</iframe>
<div class="popup_Buttons" style="display: none">
<input id="btnOkay" type="button" value="Speichern" />
<input id="btnCancel" type="button" value="Abbrechen" />
</div>
</div>
PS: And I want input in the TextBoxes in the Background if the Dialog is open.
update:
...
<asp:modalpopupextender id="ModalPopupExtender1"
runat="server" cancelcontrolid="btnCancel"
okcontrolid="btnOkay" targetcontrolid="btnAddNew"
popupcontrolid="Panel1" popupdraghandlecontrolid="PopupHeader"
drag="true" backgroundcssclass="ModalPopupBG">
</asp:modalpopupextender>
<div id="PopupHeader" style="display: none; background-color:Blue">
Benutzerinformationen
</div>
<div class="popupConfirmation" id="Panel1" style="display: none">
<iframe id="frameeditexpanse" src="ZweiteSeite.aspx" frameborder="1">
</iframe>
<div class="popup_Buttons" style="display: none">
<input id="btnOkay" type="button" value="Speichern" />
<input id="btnCancel" type="button" value="Abbrechen" />
</div>
...

Try this
<style type="text/css">
.modalPopup
{
background-color: #ffffdd;
border-width: 3px;
border-style: solid;
border-color: Gray;
padding: 3px;
width: 100%;
}
</style>
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:Button ID="btnAddNew" runat="server" Text="New Expanse" />
<cc1:ModalPopupExtender ID="ModalPopupExtender1" runat="server" CancelControlID="btnCancel"
OkControlID="btnOkay" TargetControlID="btnAddNew" PopupControlID="Panel1" PopupDragHandleControlID="PopupHeader"
Drag="true" BackgroundCssClass="ModalPopupBG">
</cc1:ModalPopupExtender>
<div class="popupConfirmation" id="Panel1" style="display: none">
<asp:Panel runat="server" ID="PopupHeader" CssClass="modalPopup">
**************** Drag me ****************
</asp:Panel>
<iframe id="frameeditexpanse" src="http://www.bing.com" frameborder="1" height="500px"
width="520px"></iframe>
<div class="popup_Buttons" style="display: none">
<input id="btnOkay" type="button" value="Speichern" />
<input id="btnCancel" type="button" value="Abbrechen" />
</div>
</div>

The answer posted by #yogi works perfectly. If there are issues, try browsing the same page in a different browser, as it works smoothly in Edge and Chrome, but Internet Explorer has issues with moving the popup around and drag/drop.

ModalPopup click twice when IFrame XPAD is on the page

I have a aspx page, with a modalpopup extender, and it's work perfect.
But I place an Iframe on the end of the page, and the modelpopup work only when I click the button twice. I can't find the answer for this problem.
<asp:UpdatePanel ID="UpdatePanel4" runat="server">
<ContentTemplate>
<div class="szamlabal14">
Csatlakozási pont:
<input type="hidden" id="hdnCsatlakozasiPontKod" runat="server" value="0" />
<asp:TextBox ID="txtCsatlakozasiPont" runat="server" Width="480" onkeydown="return false;"></asp:TextBox>
<asp:Button ID="btnCsatlakozasiPont" runat="server" Text="..." />
<cc1:ModalPopupExtender ID="mpeCsatlakozasiPont" runat="server" CancelControlID="btnCancel"
TargetControlID="btnCsatlakozasiPont" OkControlID="btnOk" PopupControlID="pnPopup"
PopupDragHandleControlID="PopupHeader" Drag="true" BackgroundCssClass="modalBackground">
</cc1:ModalPopupExtender>
<asp:Panel ID="pnPopup" Style="display: none" runat="server">
<div class="modalPopup">
<div style="position: relative; left: 670; margin: 3px;">
<asp:Button ID="btnCancel" runat="server" Text="x" CausesValidation="false" OnClientClick="return false;" />
<asp:Button ID="btnOk" runat="server" Text="Ok" Style="display: none" CausesValidation="false"
OnClientClick="return false;" />
</div>
<iframe id="ifrCsatlakozasiPont" height="350px" width="700px" src="CsatlakozasiPont.aspx"
frameborder="1"></iframe>
</div>
</asp:Panel>
</div>
</ContentTemplate>
</asp:UpdatePanel>
When I delete the following part, the modalpopup work well again.
<div style="margin-top: 10px; z-index: 10; border: 1px solid black; position: absolute;
top: 130px;">
<iframe src="http://ismts38105/viewer/ImageViewer.xbap?<%=Image%> width="1440"
height="400" />
</div>

You need to set the permissions on your Internet Explorer. XBAP requires you add the domain/IP to the trusted sites, or else you will be unable to do anything with them.

Combobox selected item is deleted once selected . Invalid Postback or Callback argument

I have four textboxes one combobox and one button ( and some other controls) in my page . Based on the values typed in the textboxes the related values are updated in the combobox. On clicking the submit button in my page It was giving the following error .
"Invalid postback or callback argument. Event validation is enabled using in configuration or in a page. For Secuity purposes,this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected . Use the ClientScriptManager.RegisterForEventsValidation method in order to register the postback or callback data for validation."
Now in the page directive I added
<%#Page EnableEentValidation="false">
When I type the values in the four textboxes the corresponding value will appear in the cobobox . But when I select that combobox value, the selected value wil be deleted . What is the reason for this ?
<%# Page Language="C#" MasterPageFile="~/Main.Master" AutoEventWireup="true" CodeBehind="AddeChecklist.aspx.cs"
Inherits="LabTrack.WebApplication.Echecklist.AddeChecklist" EnableEventValidation ="false" %>
<%# Register TagPrefix="Labinal" TagName="AutoCompleteControl" Src="~/UserControls/AutoCompleteEnabledWebUserControl.ascx" %>
<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="Server">
<link href="../Styles/CheckListRev.css" rel="stylesheet" type="text/css" />
<!-- Style for the page -->
<link href="../Styles/AddeChecklist.css" rel="stylesheet" type="text/css" />
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
<asp:ScriptManager ID="ScriptManager1" EnablePartialRendering="true" runat="server">
</asp:ScriptManager>
<asp:Panel ID="ErrorMessagePanel" CssClass="ErrorPanel" Visible="true" runat="server">
<div class="ErrorDiv">
<asp:BulletedList CssClass="ErrorMessage" ID="ErrorMessageBulletedList" runat="server">
</asp:BulletedList>
</div>
</asp:Panel>
<div class="PageTitle">
<asp:Label ID="PageHeaderLabel" runat="server"></asp:Label>
</div>
<div class="MainDiv">
<div style="text-align: center;">
<div class="PlaceHolder">
<table id="formTable">
<tr>
<td>
<asp:UpdatePanel runat="server" ID="updatepanelCustomer" UpdateMode="Conditional">
<ContentTemplate>
<span class="boldLabelLong">Customer:</span><br />
<asp:TextBox ID="CustomerNameTextBox" Width="200" runat="server"></asp:TextBox>
<asp:HiddenField ID="IxCustomerHiddenField" runat="server" />
<asp:Button ID="customerTriggerbutton" runat="server" Text="Button" Style="display: none;" />
</ContentTemplate>
</asp:UpdatePanel>
</td>
<td>
<asp:UpdatePanel runat="server" ID="updatepanelProgram" UpdateMode="Conditional">
<ContentTemplate>
<span class="boldLabelLong">Program:</span><br />
<asp:TextBox ID="ProgramNameTextBox" Width="200" runat="server"></asp:TextBox>
<asp:Button ID="programTriggerbutton" runat="server" Text="Button" Style="display: none;" />
<asp:HiddenField ID="IxProgramHiddenField" runat="server" />
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="customerTriggerbutton" EventName="Click" />
</Triggers>
</asp:UpdatePanel>
</td>
<td>
<asp:UpdatePanel runat="server" ID="updatepanelWorkPackage" UpdateMode="Conditional">
<ContentTemplate>
<span class="boldLabelLong">WorkPackage:</span><br />
<asp:TextBox ID="WorkPackageNameTextBox" Width="200" runat="server"></asp:TextBox>
<asp:HiddenField ID="IxWorkPackageHiddenField" runat="server" />
<asp:Button ID="workPackageTriggerbutton" runat="server" Text="Button" Style="display: none;" />
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="programTriggerbutton" EventName="Click" />
</Triggers>
</asp:UpdatePanel>
</td>
<td>
<asp:UpdatePanel runat="server" ID="updatepanelActivity" UpdateMode="Conditional">
<ContentTemplate>
<span class="boldLabelLong">Activity:</span><br />
<asp:TextBox ID="ActivityNameTextBox" Width="200" runat="server"></asp:TextBox>
<asp:HiddenField ID="IxActivityHiddenField" runat="server" />
<asp:Button ID="activityTriggerbutton" runat="server" Text="Button" Style="display: none;" />
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="workPackageTriggerbutton" EventName="Click" />
<asp:AsyncPostBackTrigger ControlID="activityTriggerbutton" EventName="Click" />
</Triggers>
</asp:UpdatePanel>
</td>
</tr>
</table>
</div>
<div class="PlaceHolder">
<asp:Label ID="TemplateLabel" Text="Template:" CssClass="ControlLabel" runat="server"></asp:Label>
<asp:UpdatePanel runat="server" ID="updatepanelTemplate" UpdateMode="Conditional">
<ContentTemplate>
<asp:DropDownList ID="TemplateSelectDropDownList" runat="server" Width="400" Visible="true"
AutoPostBack="true">
</asp:DropDownList>
<asp:HiddenField ID="IxTemplateHiddenField" runat="server" />
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="workPackageTriggerbutton" EventName="Click" />
</Triggers>
</asp:UpdatePanel>
<asp:Panel ID="SustainPanelTemplateOwner" Visible="true" runat="server">
<div>
<asp:Label ID="TemplateOwnerLabel" Text="Owner:" CssClass="ControlLabel" runat="server"></asp:Label>
<asp:TextBox ID="TemplateOwnerTextBox" CssClass="controlMargin" Width="400" runat="server"></asp:TextBox>
</div>
</asp:Panel>
<asp:HiddenField ID="IxDeliverableHiddenField" runat="server" />
<asp:HiddenField ID="IxReleaseActionHiddenField" runat="server" />
<asp:HiddenField ID="IxConfigHiddenField" runat="server" />
<asp:HiddenField ID="IxTemplateOwnerHiddenField" runat="server" />
<asp:HiddenField ID="TemplateSelectedSnameHiddenField" runat="server" />
<asp:HiddenField ID="TemplateOwnerSelectedsNameHiddenField" runat="server" />
<asp:HiddenField ID="DeliverableSelectedHiddenField" runat="server" />
<div>
<asp:Label ID="DeliverableLabel" CssClass="ControlLabel" runat="server" Text="Deliverable:"></asp:Label>
<asp:TextBox ID="DeliverableTextBox" CssClass="controlMargin" Width="400" runat="server"></asp:TextBox>
</div>
<asp:Panel ID="SustainPanelConfig" Visible="true" runat="server">
<div>
<asp:Label ID="ConfigurationLabel" runat="server" Text="Configuration:" CssClass="ControlLabel"></asp:Label>
<select id="ConfigurationSelect" class="controlMargin">
<option></option>
</select>
</div>
</asp:Panel>
<asp:Panel ID="SustainPanelRelease" Visible="true" runat="server">
<div>
<asp:Label ID="ReleaseActionLabel" CssClass="ControlLabel" runat="server" Text="Release Action:"></asp:Label>
<asp:TextBox ID="ReleaseActionTextBox" CssClass="controlMargin" Width="400" runat="server"></asp:TextBox>
</div>
</asp:Panel>
<asp:Panel ID="SustainPanel" Visible="true" runat="server">
<div class="SustainPanelControls">
<div>
<asp:Label ID="ChangeLabel" Text="Change #: " runat="server"></asp:Label>
</div>
<div>
<asp:TextBox ID="ChangeTextBox" Width="110" runat="server"></asp:TextBox>
</div>
<div>
<asp:Label ID="SupplementLabel" Text="Supplement: " runat="server"></asp:Label>
</div>
<div>
<asp:TextBox ID="SupplementTextBox" Width="80" runat="server"></asp:TextBox>
</div>
<div>
<asp:Label ID="NewWrrLabel" Text="WRR #: " runat="server"></asp:Label>
</div>
<div>
<asp:TextBox ID="NewWrrTextBox" Width="80" runat="server"></asp:TextBox>
</div>
<div>
<asp:Label ID="DddLabel" Text="3D: " runat="server"></asp:Label>
</div>
<div>
<asp:TextBox ID="DddTextBox" Width="80" runat="server"></asp:TextBox>
</div>
</div>
<div>
<table id="DesignDataTable2">
<tr>
<td>
<asp:Label ID="AllFbSheetsWrrLabel" Text="All F/B Sheets w/WRR #:" CssClass="ControlLabel" runat="server"></asp:Label>
</td>
<td>
<asp:TextBox CssClass="completeControl" ID="AllFbSheetsWrrTextBox" Width="588" Rows="2"
TextMode="MultiLine" runat="server"></asp:TextBox>
</td>
</tr>
</table>
</div>
</asp:Panel>
</div>
<div class="EditButtonGroup">
<input id="EditButton" type="button" value="Edit" class="ButtonSettings" />
<input id="RemoveButton" type="button" value="-" class="ButtonSettings" />
<input id="AddButton" type="button" value="+" class="ButtonSettings" />
</div>
</div>
<div class="ViewData">
<div class="ViewDataDiv">
<table id="DesignDataTable" class="designDataTable">
<tbody>
</tbody>
</table>
</div>
</div>
<div class="submitButtonDiv">
<asp:Button ID="SubmitButton" runat="server" Text="Button Text" class="submitButtonCreateChecklist" />
</div>
</div>
</asp:Content>

You are creating new values on the client side, and posting them back to the server.
For security reasons ASP.NET implements "event validation". When even validation is enabled, if the server creates a combo with 3 possible values, it will only accept this values on postback. If you create a different value and send it back to the server, you get the error you're referring to.
Here you have some info:
Page.EnableEventValidation Property
You can use ClientScriptManager.RegisterForEventValidation Method if you know which are the possible values generated on the client side, or disable validation completely if you don't know them in advance.
To disable validation:
You set the EnableEventValidation property by setting the enableEventValidation attribute of the # Page directive or the enableEventValidation attribute of the pages element in the Web.config file. If you set this property in code, you must set it before the page is initialized.

Sounds like an issue with Viewstate overriding the values.
Try fetching the value directly using Request.Form[Dropdown.ClientId]

Why does my ASP Server return this message

I have a form which I load within a modal window in that from I have used a updatepanel and a textbox named txtAccountInfo. I have set textchange event on that textbox first time change text event fired but in the second time textchange shows this message.
uncaught exception: [Exception... "'Sys.InvalidOperationException: Sys.InvalidOperationException: Could not find UpdatePanel with ID 'uppMain'. If it is being updated dynamically then it must be inside another UpdatePanel.' when calling method: [nsIDOMEventListener::handleEvent]" nsresult: "0x8057001c (NS_ERROR_XPC_JS_THREW_JS_OBJECT)" location: "JS frame :: chrome://firebug/content/spy.js :: callPageHandler :: line 744" data: no]
my ASP.Net Code
<%# Page Language="C#" AutoEventWireup="true" CodeBehind="mAddOrder.aspx.cs" Inherits="iSBBranch.ModalWindow.mAddOrder" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<style type="text/css">
</style>
</head>
<body>
<div style="width: 850px;">
<form id="form1" class="form" action="ModalWindow/mAddOrder.aspx" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:UpdatePanel ID="uppMain" UpdateMode="Conditional" runat="server">
<ContentTemplate>
<asp:HiddenField ID="txtOrderType" Value="p" runat="server" />
<asp:HiddenField ID="txtOrderStatus" Value="n" runat="server" />
<asp:HiddenField ID="txtOrderRef" runat="server" />
<fieldset id="AccountId" style="width: 783px; position:relative;">
<legend>Account Information</legend>
<p>
<label>
*Account Number </label>
<span class="relative">
<asp:TextBox ID="txtInvestorRef" CssClass="TextBox" runat="server"
OnTextChanged="txtInvestorRef_TextChanged" AutoPostBack="True"></asp:TextBox>
<span class="<%=iSBBranch.ModalWindow.mAddOrder.AccountStatus%>"></span></span>
<div style="position:absolute; right:100px; top:10px;">
<asp:UpdateProgress ID="pbContactAddress" runat="server" AssociatedUpdatePanelID="uppMain"
DisplayAfter="100" DynamicLayout="true">
<ProgressTemplate>
Loading
<img alt="Loading..." src="images/info-loader.gif" />
</ProgressTemplate>
</asp:UpdateProgress>
</div>
</fieldset>
<div class="columns">
<!-- Left column -->
<div class="colx2-left">
<fieldset>
<legend>Post Order</legend>
<p class="inline-medium-label" style="text-align: right;">
<label for="field1">
Company</label>
<asp:DropDownList CssClass="Combobox" ID="ddlCompany" runat="server" OnSelectedIndexChanged="ddlCompany_SelectedIndexChanged"
AutoPostBack="True">
</asp:DropDownList>
</p>
<br class="clear" />
<p class="inline-medium-label" style="text-align: right;">
<label for="field1">
Total Quantiy</label>
<asp:TextBox ID="txtTotalQuantity" runat="server" CssClass="NumberField" ReadOnly="true">0</asp:TextBox>
</p>
<br class="clear" />
<p class="inline-medium-label" style="text-align: right;">
<label for="field1">
Matured Balance</label>
<asp:TextBox ID="txtMaturedBalance" runat="server" CssClass="NumberField" ReadOnly="true">0</asp:TextBox>
</p>
<br class="clear" />
<p class="inline-medium-label" style="text-align: right;">
<label for="field1">
Share Quantity</label>
<asp:TextBox ID="txtShareQuantity" CssClass="NumberField" runat="server" Text="0"
OnTextChanged="txtShareQuantity_TextChanged" AutoPostBack="True"></asp:TextBox>
</p>
<br class="clear" />
<p class="inline-medium-label" style="text-align: right;">
<label for="field1">
Rate</label>
<asp:TextBox ID="txtRate" CssClass="NumberField" runat="server" OnTextChanged="txtRate_TextChanged"
AutoPostBack="True">0</asp:TextBox>
</p>
<br class="clear" />
</fieldset>
</div>
<!-- Right column -->
<div class="colx2-left" style="margin-left: 10px;">
<fieldset>
<legend>Company’s Current</legend>
<p class="inline-medium-label" style="text-align: right;">
<label for="field1">
Market Type</label>
<asp:TextBox ID="TextBox1" ReadOnly="true" CssClass="TextBox" runat="server"></asp:TextBox>
</p>
<p class="inline-medium-label" style="text-align: right;">
<label for="field1">
Last Trade Price</label>
<asp:TextBox ID="TextBox2" runat="server" CssClass="NumberField" ReadOnly="true"></asp:TextBox>
</p>
<p class="inline-medium-label" style="text-align: right;">
<label for="field1">
Market Lot</label>
<asp:TextBox ID="TextBox3" runat="server" CssClass="NumberField" ReadOnly="true"></asp:TextBox>
</p>
<p class="inline-medium-label" style="text-align: right;">
<label for="field1">
Highest Price
</label>
<asp:TextBox ID="TextBox4" runat="server" CssClass="NumberField" Enabled="false"></asp:TextBox>
</p>
<p class="inline-medium-label" style="text-align: right;">
<label for="field1">
Lowest Price</label>
<asp:TextBox ID="TextBox5" Enabled="false" CssClass="NumberField" runat="server"></asp:TextBox>
</p>
</fieldset>
</div>
</div>
<br class="clear" />
<div class="">
<fieldset style="width: 783px;">
<div style="float: right;">
<p class="inline-medium-label" style="text-align: right;">
<label>
Total Trade Amount</label>
<asp:TextBox ID="txtTotalTradeAmount" runat="server" CssClass="NumberField" ReadOnly="true"></asp:TextBox>
</p>
</div>
</fieldset>
</div>
<br class="clear" />
<div style="margin-top: 10px;">
<asp:Button ID="btnSave" CssClass="big-button" runat="server" Text="Save"
onclick="btnSave_Click" />
<asp:Button ID="Button2" OnClientClick="return $.modal.current.closeModal();" CssClass="big-button"
runat="server" Text="Close" />
</div>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="btnSave" EventName="Click" />
<%-- <asp:AsyncPostBackTrigger ControlID="txtInvestorRef" EventName="TextChanged" />--%>
</Triggers>
</asp:UpdatePanel>
</form>
</div>
<script type="text/javascript">
CenterWindow();
</script>
</body>
</html>
If I close this from and again open the from then no error shows in any times on that session.
Please advise.

Without seeing any code, this is just a guess, but this error usually means that you are trying to force one UpdatePanel to refresh from within another UpdatePanel. Are you trying to set a trigger for one, that is located within another? This is not possible.
You are also using a modal window. What are you using to render this? Is it placing the modal div within the ASP.NET form? jQuery and simpleModal do not, by default, they append it to the end of the DOM. So trying to update an UpdatePanel from inside such a dialog would also give you this error.
Please post some code and people will be able to help you better.

Try using FireBug to see if the modal window messes somehow with your updatepanel code. I might have changed the ID.