By default, HTML displays a simple hint on an element where you've set the title attribute. Look at the following code:

<a title="CMS concrete5" href="http://concrete5.org/help" target="_blank">help</a>

This will produce the following result, although the exact output might differ depending on your browser and operating system:

Again, jQuery is going to help us to customize this little information box. There's a nice jQuery plugin called TipTip from Drew Wilson which you can find here: http://code.drewwilson.com/entry/tiptip-jquery-plugin.