rich textbox disappear when i use url routing

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routing

hi,
h am using tinymce rich textbox, when i do not use url routing it works fine, but when i use it, normal textbox appear, is there any relation between routing and rich textbox ?
i am using asp.net c# and this is the code

<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="newThread.aspx.cs" Inherits="_Default" ValidateRequest="false" %>


<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
    <title>

    </title>
    
        <script type="text/javascript" src="tinymce/jscripts/tiny_mce/tiny_mce.js"></script>
    <script type="text/javascript" lang="javascript">
        tinyMCE.init({
            mode: "textareas",
            theme: "advanced",
            plugins: "pagebreak,style,layer,table,save,advhr,advimage,advlink,emotions,iespell,inlinepopups",
        });
    </script>
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
        <div id="content">
        
        <table style="width:100%;">
            <tr>
                <td style="width:100px;">العنوان:</td>
                <td>
                    <asp:TextBox ID="TextBox1" runat="server" Width="253px" AutoCompleteType="Disabled"></asp:TextBox>
                </td>
            </tr>
            <tr>
                <td>الموضوع:</td>
                <td rowspan="16">
                    <asp:TextBox ID="RichTextBox" runat="server" TextMode = "MultiLine" Width="750px" Height="406px"></asp:TextBox>

                </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td> </td>
            </tr>
            <tr>
                <td style="width:100px;">القسم:</td>
                <td>
                    <asp:DropDownList ID="DropDownList1" runat="server" Height="18px" Width="145px">
                    </asp:DropDownList>
                </td>
            </tr>
            <tr>
                <td style="width:100px;"> </td>
                <td></td>
            </tr>
            <tr>
                <td style="width:100px;">الفئة العمرية:</td>
                <td>
                    <asp:DropDownList ID="DropDownList2" runat="server" Height="16px" Width="145px">
                    </asp:DropDownList>
                </td>
            </tr>
            <tr>
                <td style="width:100px;">العنوان:</td>
                <td>
                    <asp:Button ID="Button1" runat="server" Text="اضافة" Width="145px" OnClick="Button1_Click" />
                </td>
            </tr>
            <tr>
                <td style="width:100px;"> </td>
                <td>
                    <asp:Label ID="Label3" runat="server"></asp:Label>
                </td>
            </tr>
        </table>

    </div>
</asp:Content>

thanks in advance