Have you ever heard the ThinkFreeFox -ThinkFree Firefox Extension ?
ThinkFreeFox is the extension that
user allow to view and edit the all types of documents from anywhere, at anyplace.
You don’t need to install heavy MS-Office, OpenOffice, StarOffice or anythings.
ThinkFreeFox uses leading ThinkFree viewer and ThinkFree conversion Server for its core documenation technology.
If you are using the Firefox web browser, You can view the any format of documents that are web resources.
ThinkFreeFox supports the unlimited file format like doc, docx, dot, rtf, xls, xlsx, xlt, ppt, pptx, pot, potx, pps, ppsx and hwp. Check the link https://addons.mozilla.org/en-US/firefox/addon/9327