This plugin enables you to display an auto popup / popover on the homepage of your WordPress website. It can be configured to display only once per visitor per session, and can display any webpage or image:

I've included an example webpage to show how it can be used as a Welcome Box for your visitors or first-time visitors, with the functionality to enable the visitors to opt out of seeing it on future visits:

You can choose to modify that page to suit your needs (welcomebox.php - located in the plugin's directory) or you can use any webpage you want by entering the URL on the plugin's settings page: (Note: The screenshot shows an older version of WordPress, but it works all the way up to version 3.3.2+)

It can, of course, be used to display adverts or promotions!

Tags : popover, wpopup, popups, pop-up, auto pop-up, pop over, pop-over, LightBox, Opt-in Popup, jquery popup, popup, auto popup