With Strategy Web 10.1, Flash mode for document execution and MHT export has been deprecated as outlined in KB257502: New in MicroStrategy 10.1 - Interactive and Flash document view modes deprecated.
Existing documents that have Flash mode enabled will still be executable in Flash mode and can be exported to MHT.
Users can disable or enable Flash mode on the project and user level using the Web preference > Report Services > "Enable Flash Mode".

When disabling the preference "Enable Flash Mode", documents set to run in Flash mode will execute in Presentation mode. Additionally, users will not be able to export documents to Flash.
Note: This setting has only an effect on existing documents that have Flash mode / export enabled. New documents will only run in Presentation mode.