I do not like this practice, which destabilizes the user and 90% of cases, this user does not aim to copy something on your page (text, image, ...). But my technique I use to the advantage of being very effective, unlike all the other techniques you can find on the Web (see my demo in the "/demo/" folder). This technique also provides a security if the user disables JavaScript in the Web browser.
Pierre-Henry SORIA
Attribution-ShareAlike 3.0 or later; See the LICENSE.txt file.