I'm confuse with the error "must be placed inside a form tag with runat=server."

I want to create button dynamically with this code
  Dim MyLabel(4) As Button
        Dim cnt As Byte
        Dim I As Byte
        cnt = 0
        Response.Write("<form runat='server'>")
        For I = 0 To 3           
            cnt += 25
            MyLabel(I) = New Button()
            MyLabel(I).ID = "Btn" + CStr(I)
            MyLabel(I).Text = "haha"           
   ...