You can specify the display mode. The 3 possible values are:
1) "always" - This makes the fade-in box load each time the page is displayed
2) "oncepersession" - This uses cookies to display the fade-in box only once per browser session
3) integer (ie: 5) - Finally, you can specify an integer to display the box randomly via a frequency of 1/integer...
For example, 2 would display the box about (1/2) 50% of the time the page loads.