This site has been tested in the following browsers:
Safari   -   the best
Google Chrome   -   excellent
Opera 10.51   -   excellent
Mozilla Firefox   -   adequate
IE8   -   adequate
To browse djvu, pdf and other non-text formats directly within a browser, in most cases you need plug-ins.
More information about DjVu-format - from here, you can download ExpressView Browser Plug-in (MrSID). This routine can browse djvu for Firefox, Safari, and Netscape. See also: Extended information on DjVu-format
Most of modern browsers do have the corresponding plug-in. While installing Acrobat Reader, you can choose an option to install the plug-in of Acrobat Reader for browsers.
Firefox -
Opera - see in the below (a universal plug-in for the browser).
IE - guide
Firefox -
IE - you need to have MS Office installed
Opera - see in the below (a universal plug-in for the browser).
  Specially for Opera:  
There exists a plug-in combining several plug-ins in itself (to read pdf, djvu and others). -
  Google Chrome:  
This browser is gaining popularity - see statistics If it does not nave a plug-in, it makes a download of djvu-file (or other). After that, one can open the file if a browser needed is present in the computer.