Hi,
I believe it is due to browser setting.
Generally speaking, picture files (jpg, png ...) and text files (txt, xml, ...) can be displayed in most browsers, and will be the default behavior.
More complex files like video or audio (mpg, flv ...) depends on features or extensions you have.
It makes sense that not all files can be opened in browser.
If you want to force download all files, you can make HTML links like this:
To do this, you will need to make a separate HTML widget + JS widget to inject the HTML code dynamically.
Best regards,
Taka