Look at the following MSDN article About support for ASP.NET controls:

http://support.microsoft.com/default.aspx?scid=KB;en-us;328046

>hi Cathi,
>
>sorry just got back and read ur post..thanks for advise. The article really help, but every time i want to make a tree view there's an error message telling me "Microsoft® Internet Explorer WebControls are not currently supported." and required Microsoft.Web.UI.WebControls.dll needed
>
>anyone know how to solve this problem an how do i get Microsoft.Web.UI.WebControls.dll files ??
>
>TIA
>
>Budi