What happens if you link to a downloadable file can often be unpredictable; Firefox on OS X will merely download the file. Internet Explorer on the other hand – even on a system that has Office 2007 installed – will attempt to treat the file as a compressed file.

Download dialog showing incorrect file type

Once you choose save in Internet Explorer, it saves it as a compressed file which when you open it gives you a set of resources, similar to a Mac Bundle. It’s pretty hard to actually get the correct application to launch and run the file as it should (the example above was a PowerPoint pptx file).

Luckily, help is at hand and all you really need to do is register the new Mime types with Apache. You can either do this at the server level in the Apache configuration file, or on a per-site basis using a .htaccess file.

Apache config file
This file is called httpd.conf for Apache 1 and apache2.conf on Apache 2. There are a number of places it can be so it’s best to run a file search on the server to find it.

SSH into your server as root (if possible)
Run the command  find / -name apache2.conf or    find / -name httpd.conf
You should now see a file listing which will give you a clue as to where the file will be (most likely etc/apache2 for Apache 2 web servers).
Edit the file using the command vi /etc/apache2/apache2.conf (if that’s where the file is)
Type :10000 to jump to line 10000 (and therefore the end of the file)
Press I to insert and then newline
Paste in the following lines:

AddType application/vnd.ms-word.document.macroEnabled.12 .docm
AddType application/vnd.openxmlformats .docx .pptx .xlsx
#AddType application/vnd.openxmlformats-officedocument.presentationml.presentation .pptx
#AddType application/vnd.openxmlformats-officedocument.spreadsheetml.sheet .xlsx
AddType application/vnd.openxmlformats-officedocument.wordprocessingml.document .docx
AddType application/vnd.ms-word.template.macroEnabled.12 .dotm
AddType application/vnd.openxmlformats-officedocument.wordprocessingml.template .dotx
AddType application/vnd.ms-powerpoint.template.macroEnabled.12 .potm
AddType application/vnd.openxmlformats-officedocument.presentationml.template .potx
AddType application/vnd.ms-powerpoint.addin.macroEnabled.12 .ppam
AddType application/vnd.ms-powerpoint.slideshow.macroEnabled.12 .ppsm
AddType application/vnd.openxmlformats-officedocument.presentationml.slideshow .ppsx
AddType application/vnd.ms-powerpoint.presentation.macroEnabled.12 .pptm
AddType application/vnd.ms-excel.addin.macroEnabled.12 .xlam
AddType application/vnd.ms-excel.sheet.binary.macroEnabled.12 .xlsb
AddType application/vnd.ms-excel.sheet.macroEnabled.12 .xlsm
AddType application/vnd.ms-excel .xlt .xla
AddType application/vnd.openxmlformats-officedocument.spreadsheetml.template .xltx
AddType application/vnd.ms-excel.template.macroEnabled.12 .xltm
AddType application/vnd.ms-xpsdocument .xps
AddType application/application/vnd.ms-powerpoint .ppt .pot .pps .ppa
AddType application/msword .doc .dot

Now hit [Esc] to leave insert mode
Type :wq! to save the file
Finally restart the apache server, most likely by using the command /etc/init.d/apache2 restart
Your entire web server should now be able to deliver the correct file types – problem no more.
Per site .htaccess configuration
Browse to your remote site and open the .htaccess file if it’s present (make sure that your web / ftp client can see hidden files as dot-prefixed files are traditionally hidden from view on the Linux / Unix platform.

Create a new file if there isn’t one present and then simply add in the following lines:

AddType application/vnd.ms-word.document.macroEnabled.12 .docm
AddType application/vnd.openxmlformats .docx .pptx .xlsx
#AddType application/vnd.openxmlformats-officedocument.presentationml.presentation .pptx
#AddType application/vnd.openxmlformats-officedocument.spreadsheetml.sheet .xlsx
AddType application/vnd.openxmlformats-officedocument.wordprocessingml.document .docx
AddType application/vnd.ms-word.template.macroEnabled.12 .dotm
AddType application/vnd.openxmlformats-officedocument.wordprocessingml.template .dotx
AddType application/vnd.ms-powerpoint.template.macroEnabled.12 .potm
AddType application/vnd.openxmlformats-officedocument.presentationml.template .potx
AddType application/vnd.ms-powerpoint.addin.macroEnabled.12 .ppam
AddType application/vnd.ms-powerpoint.slideshow.macroEnabled.12 .ppsm
AddType application/vnd.openxmlformats-officedocument.presentationml.slideshow .ppsx
AddType application/vnd.ms-powerpoint.presentation.macroEnabled.12 .pptm
AddType application/vnd.ms-excel.addin.macroEnabled.12 .xlam
AddType application/vnd.ms-excel.sheet.binary.macroEnabled.12 .xlsb
AddType application/vnd.ms-excel.sheet.macroEnabled.12 .xlsm
AddType application/vnd.ms-excel .xlt .xla
AddType application/vnd.openxmlformats-officedocument.spreadsheetml.template .xltx
AddType application/vnd.ms-excel.template.macroEnabled.12 .xltm
AddType application/vnd.ms-xpsdocument .xps
AddType application/application/vnd.ms-powerpoint .ppt .pot .pps .ppa
AddType application/msword .doc .dot

save the .htaccess file and your web site should start delivering the correct file types!

Now in pptx format!