In case you are trying to provide users a download link to an APK file hosted in your server, remember to add the MIME Type to your OHS (Oracle HTTP Server) configuration. The steps to add a MIME Type are well documented, and all you need to do is to specify the correcty definition:
(step-by-step on OHS 11g)
4.4.2.1.1 Using Fusion Middleware Control to Configure MIME Types
To configure a MIME type using Fusion Middleware Control, do the following:
Select Administration from the Oracle HTTP Server menu.
Select MIME Configuration from the Administration menu. The MIME configuration page appears.
Click Add Row in MIME Configuration region. A new, blank row is added to the list.
Enter the MIME type. ---> application/vnd.android.package-archive
Enter the file extension.
Review the settings. If the settings are correct, click Apply to apply the changes. If the settings are incorrect, or you decide to not apply the changes, click Revert to return to the original settings.
Restart Oracle HTTP Server, as described in Section 4.1.4.
APK MIME Type
application/vnd.android.package-archive
That's all!