Ten years back, interstitial pages used to be almost customary. Many websites had their logos, special announcements or even advertisements displayed at the interstitial page right after you visited the respective domain. Interstitials were set to automatically redirect to the requested page after some time (generally 10 seconds) via META refresh tag.
The custom to display a (not requested) page in-between was quite intrusive and pages with advertisements often featured Flash banner over the whole page. Some website owners later started to put a “skip intro” link below the image/advertisement, but often this link was below the fold and required further action by user (scrolling and clicking) to get to the desired page.
Not only went the interstititals against usability principles, they often meant certain exit (as we call it today) or loss of a user. Many users could have felt lost or even unwelcome seeing some unfamiliar page displayed after typing the well-known URL or clicking on the link.
I haven’t seen an interstitial page for a long time now thanks to the wise website owners. Unfortunately, there are still some questionable ways to display unwanted content to the user – lightbox and its clones have been misused for this purpose over the last few years. We probably won’t see an end of this technique soon, but those interested in their visitors already know that forcing user to view unsolicited content (even worse: animated Flash banner) means bad user experience and very likely higher bounce rate (percentage of users that immediately leave).