Browsers

[Andy™]

I can only imagine that with the power lead in there is some residual voltage on the circuit boards .

yep, the PSU will always be supplying power to the motherboard even if the PC is off / standby

 

[Evans Electric]

There you go then !    I see it much like a relay with voltage on the coil that shouldn't be there .              ( Only in solid state switching ...a gate  is held open until you remove all voltage. )

 

[Ketty]

Remove all cookies, history of the browser, all temp file, prefetch file and clean register log. I think they will be fine then.