My ASP csv download page is calling: Response.Clear Response.AddHeader "content-disposition","attachment; filename=filename.csv" Response.ContentType = "Content-Type: text/csv; charset=utf-8" When I click on the link to this ASP page the Firefox "Opening filename.csv" dialog appears: filename.csv which is a: Text Document If I choose "Open with <Any Application name>" the file is always opened by the application with a .txt appended to the filename, which in this particular case prevents my spreadsheet software from correctly opening it. a) How do I prevent the .txt being appended to the file name if OpenWith is used? b) Is there a way to add a CSV type to the Tools->Options Applications Content Type list to prevent the "which is a: Text Document" message? This behaviour does not happen in Chrome, Opera, Safari or IE.