How to enable popup windows to appear in a certain location on a web page

Refer to the economist site and popup windows appear at the bottom of the page to enable you to subscribe to the site. Similarly othe开发者_开发知识库r sites have promotional items popup mostly from the bottom of the page at random times. What control should I use to enable this?

You can use a jQuery UI Dialog with the position option set to the location where you want the dialog to be displayed. Check this URL: http://jqueryui.com/demos/dialog/#option-position