When I open Tools > Options > Applications and enter csv in the search box, I see two entries for Microsoft Excel Comma Separated Values File. These correspond to "application/csv" and "text/csv". I assume Firefox found these in the registry, but that's just a guess.

Are you missing both of those?

Usually you can add a new type and an application to handle it by accessing a file with the content type (MIME type) and responding to the dialog asking what to do with the file.

Does that help?

Yes, I am missing both of entries. I'll have to experiment a bit. I'll let you know how I make out. thanks

If the server sends the .csv file with a registered MIME type then Firefox should allow to set an automatic action for that file.

You can also look at this extension from White Alice0775:

• MIME Edit: http://space.geocities.yahoo.co.jp/gl/alice0775/view/20080912/1221150790