In 2012 ICO announced that all websites that operate in the EU and UK must announce the cookies which they use which could be from Google Analytics, Google Adsense and login forms. This handy little module combats this problem with a full fledged set of features in a lightweight module.
Using the latest editions of Twitter's own Bootstrap which is integrated to the core of Joomla 3.x you'll be able to display a simple yet effective cookie notification banner knowing that it's not going to slow down your site performance.
Once the close button is clicked the module will then not display again to that user. Don't forget because the banner runs off bootstrap it will work out of the box with responsive templates!