It is common practice to place downloadable files on web sites, but Word documents, Excel spreadsheets or other files should not be the primary file format being served up to end users.
Providing file size and type information better prepares the users for downloads of these alternative formats, allowing them to make an informed decision about how they want to deal with it, i.e. load it within their browser plug-in, save it for offline viewing in a stand-alone application, or download it at a later time. For example:
"This research paper is also available in the PDF file format: Micro-economics and Student interactions (548 KB)"
"The music faculty also recorded selections from their latest concert, which is available for download: Beethoven Symphony #9 (MP3 format, 39,235 KB)"
This ensures that the person using the page has all the appropriate tools they need for proper viewing. In the case where a plug-in is not available for a specific browser or platform, this compatibility must be indicated on the web page. Authors must never assume that plug-ins, such as Acrobat Reader, are pre-installed on an end user's machine; providing a link to this helper application makes acquisition that much easer for the end user.