Macbook running OS-X 10.6.
When online via Safari I experience erratic mouse movements apparently unrelated to my own inputs. Normally I would suspect the mouse (I only have one, a Mikom optical) but I had similar problems just days ago on my other (Windows 8.1) laptop, and the cursor actually started opening programs and using controls. That laptop (the Windows one) died during my attempts to solve the problem.
I must admit that since having similar problems on two laptops I'm not longer sure which events happened on which machine. For certain though I had problems with both, and on the current (Macbook) machine the erratic cursor problem persists.
I'd be grateful for advice from any expert.