This plugin provides an overlay for each website user to confirm his age (or different things – the text is fully costomizable in the options). On right answer, a cookie is set to remember the user for a set amount of days and not show the nag screen again. Otherwise, a custom message is shown to the user and the access to the site is not granted.
The plugin was initially developed for the age restriction of selling alcoholic beverages in a webshop. Due to legal reasons, such an age restriction must be in place (depending of the country of operation).