在Firefox中需要把filename 用双引号包起来，才能得到想要的名字，不然如果含有空格，会丢掉空格后面的部分。
而IE会把空格转为_,因此也需要HttpUtility.UrlPathEncode方法处理下名字。
如果Firefox中也用HttpUtility.UrlPathEncode处理名字，空格将被替换成"%20".

 1              HttpContext.Current.Response.Buffer = true;

              HttpContext.Current.Response.ClearContent();

              HttpContext.Current.Response.ClearHeaders();

              HttpContext.Current.Response.ContentType = "Application/pdf";

              string doc1 = System.IO.Path.GetFileNameWithoutExtension(doc) + "_" + intNewID.ToString() + ".pdf";

              if(HttpContext.Current.Request.Browser.Browser != "IE")

                  HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=\"" +doc1+"\"");

              else

             HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename="+ HttpUtility.UrlPathEncode( doc1));

             byte[] buffer=System.IO.File.ReadAllBytes(doc);

             HttpContext.Current.Response.AddHeader("Content-Length", buffer.Length.ToString());

             HttpContext.Current.Response.BinaryWrite(buffer);