With a browser, how do I know which decimal separator does the operating system use?

Question

I\'m developing a web application.

I need to display some decimal data correctly so that it can be copied and pasted into a certain GUI application that

Answer 1

"Is there any way to do it on server side (preferably, so that I can collect statistics), or on client side?"

No you can't. That GUI is looking at some user or machine specific settings. First, you probably do not know at what settings this UI is looking. Second, with a webapplication you will probably not be able to check these settings (clientside --> Javacsript).