FreeTextBox has not been correctly installed. To install FreeTextBox either:
(1) add a reference to FtbWebResource.axd in web.config:
<system.web>
<httpHandlers>
<add verb="GET"
path="FtbWebResource.axd"
type="FreeTextBoxControls.AssemblyResourceHandler, FreeTextBox" />
</httpHandlers>
</system.web>
(2) Save the FreeTextBox image and javascript files to a location on your website and set up FreeTextBox as follows
<FTB:FreeTextBox id="FreeTextBox1" SupportFolder="ftbfileslocation" JavaScriptLocation="ExternalFile" ButtonImagesLocation="ExternalFile" ToolbarImagesLocation="ExternalFile" ButtonImagesLocation="ExternalFile" runat="server" />