Browsers can read plain text documents (unformatted; aka ASCII or DOS), HTML text files (formatted text and clickable text), graphics and image files, sound files, video files, streaming audio and video filesd, animation files, and PDF files.
(see Interlit Website, Chapter 12 http://www.udel.edu/interlit/chapter12.html

Browsers have applets that will play many types of files besides webpages. Try these:

Sounds | Sounds | Sounds |PowerPoint | jpeg | animated Gif | Gif | program | Motion Picture | program | screensaver install | PDF

Here is a great link to look up file types and the associated software or technology they are created with. FileInfo.com