First, some basic definitions and facts. DVI is the output format produced by TeX, the premier system for typesetting mathematical material. PostScript is the standard control language for laser printers, and can also be read on-screen by programs such as GhostView. PDF is the format read by the increasingly popular Acrobat viewer.
Most often a .dvi file is converted to a .ps (PostScript) file before printing. Frequently a .ps file is converted to a .pdf file for viewing on-screen. However, .dvi files are smaller than the corresponding .ps and .pdf files, so there are advantages in download time and disk space in using .dvi files directly for Web display.
On most TAMU computer systems (including all in the math department) the Web browser is configured to read DVI with a "helper application" such as XDVI (on Unix systems). To read DVI files on your own PC, however, you need to get and install your own such DVI viewer. Here are several essentially free ones: (I am personally familiar only with the first two on the list. Items 4-6 were noted by Brian Sladecek via Professor R. Lorentz, who says "the first two [4 and 5] seem easier to install.")
if +%PK_DEV%==+ goto UNKNOWN
in the file GENPK.BAT (which the installation script will have put in your \WINDOWS directory). (Type "REM" at the beginning of the line.)