• Tell people how large the file is so they can decide whether or not to download it. Identify the typical download time for a common speed, such as 56k. If a file is particularly big, warn people: Large!
• Identify the file format (wav, tar, whatever), so the users can tell, in advance, whether they have the software to view the file. Use the name of the most common application that a person might use to view or print the file.
• Offer a link to a utility that can display the file, if an ordinary browser cannot display the contents without supporting software such as Adobe Acrobat Reader, or a Microsoft Office application.

Inform users of the content and size of media objects. … Include the file size, the media type, and a description of the subject matter. … This information will help users determine whether they want to wait for the download. —IBM (1999)

Warn people before long downloads. Attention may wander during delays as brief as 1 second. Delays of more than 10 seconds will almost certainly lead to attention loss. … Provide download and page-load status indicators…. Expectations about content quality, relevance, and action complexity affect willingness to wait for a sequence or page to load. —Microsoft (2000)

See: IBM (1999), Microsoft (2000), Nielsen (1999f), W3C (1999)

Examples