Sitewide Splash page?

Question

http://webscom.zendesk.com/entries/10272…
http://www.dynamicdrive.com/dynamicindex…
Those are two tutorials that tell me how to make a splash page. What I want to do though is show a splash page whenever a user comes to my site through ANY link. So they could type in my site and they'll see it, or click on a link to some forum post and they'll still see it. I figured you would just have to set cookie variables and have them be cleared whenever somebody leaves the site. But I don't know how to do that. Can anybody help me with this?
P.S. I was told it might be possible to do with .htaccess, I'll take any way I can find.

Answer 1

I had a feeling this thread would be full of lectures stating why you shouldn't do it. Here's how:
Create cookie using js, php, or whatever. Include in each page if/else where if cookie is set then show page else show splash page, redirect to splash page, or whatever.
The problem with other methods mentioned is there's no way to redirect back to the original intended page. If you include if/else to check if cookie is set and if it isn't then put an include to show the splash page then when someone clicks ok it can set a cookie and refresh the page to show the page as intended without the splash. There's plenty of information on the internets that will show you how to set a cookie and how to check if a cookie is set and do something if a cookie isn't set. Keywords to search have been bolded for you. You can also check out: http://www.w3schools.com/PHP/php_cookies.asp
Check it out if you still feel like this is something you want to do, disregarding the finger waving lecture of others.
best,
Shocker