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;
 2            HttpContext.Current.Response.ClearContent();
 3            HttpContext.Current.Response.ClearHeaders();
 4            HttpContext.Current.Response.ContentType = "Application/pdf";
 5            string doc1 = System.IO.Path.GetFileNameWithoutExtension(doc) + "_" + intNewID.ToString() + ".pdf";
 6            
 7            if(HttpContext.Current.Request.Browser.Browser != "IE")
 8                HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=\"" +doc1+"\"");
 9            else
10            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename="+ HttpUtility.UrlPathEncode( doc1));
11            byte[] buffer=System.IO.File.ReadAllBytes(doc);
12            HttpContext.Current.Response.AddHeader("Content-Length", buffer.Length.ToString());
13            HttpContext.Current.Response.BinaryWrite(buffer);

Firefox does not handle filenames with spaces . When a user clicks on an attachment with spaces, the filename is truncated to the first whitespace. While IE & Safari both handle this, Firefox refuses to accept mime headers with unquoted filename parameters. According to Firefox's bugzilla/knowledgebase, Firefox's behavior is the correct behavior and it's a problem with most webservers or web applications. This problem can be easily corrected by surrounding the filename parameter with double quotes.