mm-keep-viewer-alive-types

mm-keep-viewer-alive-types is a variable defined in `mm-decode.el'.
Its value is

("application/postscript" "application/msword" "application/vnd.ms-excel" "application/pdf" "application/x-dvi")

Documentation:
List of media types for which the external viewer will not be killed
when selecting a different article.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.