You can play a sound effect when a person rolls over an image or text or when click on a button.
Just as you created a link to open a new browser, you can also create a link to close your browser as well. Generally, the "Close Window" link is at the bottom of the pop up page but you're welcome to put it anywhere you like.
Last update date ... to know if the information is up-to-date....
A good application of layers....
Image Maps.... How to make an image your navigation panel...
Pop-Up browser window is very simple to do....