.NET上传出错。RunTime Error

在本地测试无问题，本地架设IIS别人远程上传无问题。传进FTP服务器就不能上传了（网站FCK编辑器可上传）。
错误为：
Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.

Details: To enable the details of this specific error message to be viewable on remote machines, please create a <customErrors> tag within a "web.config" configuration file located in the root directory of the current web application. This <customErrors> tag should then have its "mode" attribute set to "Off".

<!-- Web.Config Configuration File -->

<configuration>
<system.web>
<customErrors mode="Off"/>
</system.web>
</configuration>

Notes: The current error page you are seeing can be replaced by a custom error page by modifying the "defaultRedirect" attribute of the application's <customErrors> configuration tag to point to a custom error page URL.

<!-- Web.Config Configuration File -->

<configuration>
<system.web>
<customErrors mode="RemoteOnly" defaultRedirect="mycustompage.htm"/>
</system.web>
</configuration>

Server Error in '/' Application.
下面是我上传的代码

protected void Button1_Click(object sender, EventArgs e)

    {

        if (FileUpload1.HasFile)

        {

            string fileContentType = FileUpload1.PostedFile.ContentType;

            if (fileContentType == "image/bmp" || fileContentType == "image/gif" || fileContentType == "image/pjpeg")

            {

                string name = FileUpload1.PostedFile.FileName; // 客户端文件路径



                FileInfo file = new FileInfo(name);

                string fileName = file.Name; // 文件名称

                string fileName_s = "s_" + file.Name; // 缩略图文件名称

                string fileName_sy = "sy_" + file.Name; // 水印图文件名称（文字）

                string fileName_syp = "syp_" + file.Name; // 水印图文件名称（图片）



                DateTime dt = DateTime.Today;

                string filePath = string.Format("../file/{0}/{1}/{2}/", 

                    dt.Year.ToString(), dt.Month.ToString(),dt.Day.ToString());



                string webFilePath = Server.MapPath(filePath + fileName); // 服务器端文件路径

                string webFilePath_s = Server.MapPath(filePath + fileName_s);  // 服务器端缩略图路径

                string webFilePath_sy = Server.MapPath(filePath + fileName_sy); // 服务器端带水印图路径(文字)

                string webFilePath_syp = Server.MapPath(filePath + fileName_syp); // 服务器端带水印图路径(图片)

                string webFilePath_sypf = Server.MapPath("file/shuiyin.jpg"); // 服务器端水印图路径(图片)

                if (!Directory.Exists(Server.MapPath(filePath)))

                {

                    Directory.CreateDirectory(Server.MapPath(filePath));

                }



                if (!File.Exists(webFilePath))

                {

                    try

                    {

                        FileUpload1.SaveAs(webFilePath); // 使用 SaveAs 方法保存文件

                        //AddShuiYinWord(webFilePath, webFilePath_sy);

                        //AddShuiYinPic(webFilePath, webFilePath_syp, webFilePath_sypf);

                        MakeThumbnail(webFilePath, webFilePath_s, 130, 130, "Cut"); // 生成缩略图方法

                        string a = "提示：文件“" + fileName + "”成功上传，并生成“" + fileName_s + "”缩略图，文件类型为：" + FileUpload1.PostedFile.ContentType + "，文件大小为：" + FileUpload1.PostedFile.ContentLength + "B";



                        Response.Write("<script language=javascript>alert('" + a + "')</script>");



                        Image1.ImageUrl = filePath + fileName;

                        rblImgUrl.Items.Add(new ListItem(

                            "<img src=\"" + filePath + fileName_s + "\" />",

                            filePath + fileName));                       

                    }

                    catch (Exception ex)

                    {

                        string a = "提示：文件上传失败，失败原因：" + ex.Message;

                        Response.Write("<script language=javascript>alert('" + a + "')</script>");

                    }

                }

                else

                {

                    string a = "提示：文件已经存在，请重命名后上传";

                    Response.Write("<script language=javascript>alert('" + a + "')</script>");

                }

            }

            else

            {

                string  a = "提示：文件类型不符";

                Response.Write("<script language=javascript>alert('" + a + "')</script>");

            }

        }

    }

    public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)

    {

        System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);



        int towidth = width;

        int toheight = height;



        int x = 0;

        int y = 0;

        int ow = originalImage.Width;

        int oh = originalImage.Height;



        switch (mode)

        {

            case "HW"://指定高宽缩放（可能变形） 

                break;

            case "W"://指定宽，高按比例 

                toheight = originalImage.Height * width / originalImage.Width;

                break;

            case "H"://指定高，宽按比例

                towidth = originalImage.Width * height / originalImage.Height;

                break;

            case "Cut"://指定高宽裁减（不变形） 

                if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)

                {

                    oh = originalImage.Height;

                    ow = originalImage.Height * towidth / toheight;

                    y = 0;

                    x = (originalImage.Width - ow) / 2;

                }

                else

                {

                    ow = originalImage.Width;

                    oh = originalImage.Width * height / towidth;

                    x = 0;

                    y = (originalImage.Height - oh) / 2;

                }

                break;

            default:

                break;

        }



        //新建一个bmp图片

        System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);



        //新建一个画板

        System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);

        //设置高质量插值法

        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;



        //设置高质量,低速度呈现平滑程度

        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;



        //清空画布并以透明背景色填充

        g.Clear(System.Drawing.Color.Transparent);



        //在指定位置并且按指定大小绘制原图片的指定部分

        g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight),

        new System.Drawing.Rectangle(x, y, ow, oh),

        System.Drawing.GraphicsUnit.Pixel);



        try

        {

            //以jpg格式保存缩略图

            bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);

        }

        catch (System.Exception e)

        {

            throw e;

        }

        finally

        {

            originalImage.Dispose();

            bitmap.Dispose();

            g.Dispose();

        }

    }