All open application icons accidentally removed from task bar! D'OH!

I have accidentally caused all the open application icons, that usually display on the task bar and allow me to easily switch to them, to be removed from the task bar! Things like Dolphin, Konsole, Firefox, etc. Self-inflicted.

I was only trying to remove a single (not yet open/running), doubled-up, application icon when this strangely occurred, I don't know how it happened, nor how to rectify my error.

Any help greatly accepted.

(Currently my feet are full of holes!)