How to implement a banner

I have a need to display a banner, preferably at the bottom of the page, that remains displayed on the page regardless of where they might navigate. It isn't needed if they click on a link that open a new window such as when creating an opportunity but fine if it is displayed. Is this possible and any direction toward how to implement such an item is appreciated. I do know I can setup an alert that appears when they login and they can click off of it. The need is for the banner to