Missing a using directive or assembly reference

Hello, I have the following build error in my project:

Error    3    The type or namespace name 'IAccountService' could not be found (are you missing a using directive or an assembly reference?)    C:\Projects\Forestry\Forestry\Presenter\LoginPresenter.cs    23    17    Forestry
here is my LoginPresenter code:
using System;
using System.Data;
using System.Configuration;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using School.SchoolLibrary;
using School.SchoolLibrary.Impl;
using School.Forestry.Interface;
using StructureMap;

namespace School.Forestry.Presenter
{
&nb ...