I recently built a Drupal site on an Apache server setup and everything seemed fine until someone running IE8 tried to download a .docx file. For some reason IE8 insisted that this file was a .zip file and would open it as such, causing a bit of confusion as to what the problem was. I assumed that this was due to the mime type of the file not being set properly, but I decided to do a quick search to see if I could find anything to corroborate this. I thought it might be something odd that IE8 was doing as everything else was downloading the file perfectly.
After wading through multiple support forums and finding very little of any help I eventually gave up and went with my first hunch and set the mime type for the .docx file extension in the sites .htaccess file. Here is the rule I used:
AddType application/vnd.openxmlformats-officedocument.wordprocessingml.document docx
This solved the problem right away. To cover my bases for any future idiocy from IE8 I thought it might be good to set up some other mime types for Microsoft Office files. Here is the final list:
AddType application/vnd.ms-word.document.macroEnabled.12 .docm AddType application/vnd.openxmlformats-officedocument.wordprocessingml.document docx 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.openxmlformats-officedocument.presentationml.presentation pptx 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.openxmlformats-officedocument.spreadsheetml.sheet xlsx AddType application/vnd.ms-excel.template.macroEnabled.12 xltm AddType application/vnd.openxmlformats-officedocument.spreadsheetml.template xltx
Just drop this into your .htaccess file or your mime.types file to get IE8 to correctly download the files.