Background: For whatever reason, each time a user attempts to open an xslx (stand out 2007) file from your intranet using MSIE, the file download dialog translates it as being a "zip" file.

Of course, xslx files really are zip files, but we do not want that behavior. Just open in Stand out, please.

Question:

Opera, OTOH, opens the files normally. Is it feasible the fault is my apache configs? or perhaps is mtss is a client-browser-only problem?

This is because IE's strange MIME sniffing at behavior: http://msdn.microsoft.com/en-us/library/ms775147.aspx. It essentially attempts to determine towards the file kind of personal files by considering its contents, in some way like Linux's file tool.

You have to then add new MIME-TYPES on the internet-server-side.

Begin to see the comment-thread on this windowsnerd.com page (from 2009):

Add this to some .htaccess file and throw it in your site: AddType application/vnd.openxmlformats .docx .pptx .xlsx .xltx . xltm .dotx .potx .ppsx

Should fix most of the problems.

Alternatively, you can include this towards the mime.types file situated within the config directory of the Apache web server

application/vnd.ms-word.document.macroEnabled.12 .docm
application/vnd.openxmlformats-officedocument.wordprocessingml.document docx
application/vnd.openxmlformats-officedocument.wordprocessingml.template dotx
application/vnd.ms-powerpoint.template.macroEnabled.12 potm
application/vnd.openxmlformats-officedocument.presentationml.template potx
application/vnd.ms-powerpoint.addin.macroEnabled.12 ppam
application/vnd.ms-powerpoint.slideshow.macroEnabled.12 ppsm
application/vnd.openxmlformats-officedocument.presentationml.slideshow ppsx
application/vnd.ms-powerpoint.presentation.macroEnabled.12 pptm
application/vnd.openxmlformats-officedocument.presentationml.presentation pptx
application/vnd.ms-excel.addin.macroEnabled.12 xlam
application/vnd.ms-excel.sheet.binary.macroEnabled.12 xlsb
application/vnd.ms-excel.sheet.macroEnabled.12 xlsm
application/vnd.openxmlformats-officedocument.spreadsheetml.sheet xlsx
application/vnd.ms-excel.template.macroEnabled.12 xltm

http://www.webdeveloper.com/forum/showthread.php?t=162526