Understanding User and Kernel Mode

Actually, I’ve heard some places used TUX to serve out static advertising landing pages for URLs they were sitting on, and I guess between the falling cost of hardware and the failing interest of kernel devs to touch it, TUX fell out of interest.

But this nonsense about software exception handling needs explanation. Between the intended audience (programmers who somehow don’t understand userspace / kernel space divisions) and the very light detail given, I can only assume for the moment that the statement about implying kernel transitions is bwrong/b.