Problem

* How do you make a file download cause a save-as prompt rather than displaying the file?

Resolution

-- You use the 'Add HTTP Header' filter to send a Content-disposition header:

Content-disposition: attachment; filename=readme.txt

The header itself is described in RFC 2616 Section 19.5.1, but there are small differences in behavior depending on which browser you use. A site called Greenbytes maintains a thorough list of known browser differences.