There's a special place...
…in hell for designers and business-types who feel the need to put full-screen advertisements before the website. The same goes to those who put random ads in the way while navigating between two pages, though perhaps these do not end up quite as deep.
I understand the motivation: full-screen advertisements can pull in far more revenue than gutter ads or even banner ads, just like full-page ads in a newspaper pull in far more than classifieds. But no newspaper would put a full-page ad on the front page. (Frankly, newspapers don’t put any ads on their front pages.)
So, what? This isn’t print. Well, let’s look at, by far, the most successful advertising model on the internet: Google. Google has essentially made a multi-billion-dollar market out of classified ads. Unobtrusive, text-based ads appear around your search results or, thanks to the AdSense program, on various third-party sites.
Meanwhile, visitors coming to your site, probably from Google, are coming face-to-face with the latest movie poster, only to turn around and go back to Google and the next result in the list.
So, please, ignore your advertising department’s pleas to put up splash-page ads, and remember that conversion rate is far more important than forcing a pay-per-click splash-screen on unsuspecting visitors.