Multimedia/Internet keys are additional function keys on PC keyboards that either invoke specific applications like browser, e-mail, media player, etc. or invoked certain function for these applications. They are to be distinguished from ordinary function keys as they are labelled with specific tasks like opening a URL, changing sound volume or alike.
They did show up in great numbers in late 1998 and brought a certain hype, which faded fast in the early 2000s. Here's an especially 'pretty' unit:
Not only featuring multimedia keys and many labels, but as well made with a case copying the translucent style made popular by the G3 IMac ... another hype of the late 1998,
Technical they were simply additional scancodes handled by Windows (or background in general) to start either application/bring it to foreground or be forwarded to the fitting application as messages to invoke functions.
Question: Which were the first keyboards to include dedicated keys to invoke an internet browser and/or similar functions.
So far everything I know points to Microsoft (see "Answer" below), but was there anyone going that way before or was it really MS' hardware department that started all of this?
Please Note: This question is about keyboards (PS/2, USB) for IBM PC compatible machines and Windows and focuses on browser invocation. I don't mind additional information, but only if they fit the basic idea, so Commodore's Plus4 should not apply.