Here is a pretty good tutorial on
cookies in JavaScript. Read, set, delete, etc.
Basically, I guess the index page would contain the splash screen. Before the splash screen displays, check for the EXISTENCE of the cookie - if there isn't one, write the cookie (name it "splash") and give it a value of 1, then display the splash. If there IS a cookie, check the value - if it's less than 3, display the splash and add 1 to the value of the splash cookie. If it's greater than 3, don't display the splash (I guess a redirect before the splash displays would prevent it from showing.) A simple "IF" conditional can determine whether to show the splash page or redirect to another URL.