Web Forms :: HTML Input Tag Is Adding 2 Times While Saving The Aspx.page

I have 1 aspx page.In that i am using Developer Express controls also. If i do some changes in that page and trying to save, only the HTML input tags are repeating 2 times.

<dx:TabPage Text="Guarantor"> --using Devxpress tab control here
<ActiveTabStyle BackColor="#FF8888">
</ActiveTabStyle>
<TabStyle BackColor="#F2F7FA">
</TabStyle>
<ContentCollection>
<dx:ContentControl ID="ContentControl2" runat="server" SupportsDisabledAttribute="True">
<table style="width: 883px" border="2">
<tr>
<td bgcolor="WhiteSmoke">
<asp:Label ID="lblPrefix" runat="server" Text="Prefix" CssClass="label"></asp:Label>
</td>
<td bgcolor="WhiteSmoke">
<asp:DropDownList ID="ddlPrefix" runat="server" Height="21px"
Width="127px">
</asp:DropDownList>
</td>
<td bgcolor="WhiteSmoke">
<asp:Label ID="lblSSN" runat="server" CssClass="label" Text="SSN"></asp:Label>
</td>
<td bgcolor="WhiteSmoke">
<input type="text" id="txtSSN" runat="server" onkeydown="ssn(this.id)" onkeyup="ssn(this.id)" />
<input id="txtSSN" runat="server" onkeyup="ssn(this.id)" /> --2nd time appear here
</td>
<td bgcolor="WhiteSmoke">
<asp:Label ID="lblGender" runat="server" CssClass="label" Text="Gender"></asp:Label>
</td>
<td width="147" bgcolor="WhiteSmoke">
<asp:DropDownList ID="ddlGender" runat="server" Height="21px"
Width="127px">
</asp:DropDownList>
</td>