Interstitial ad appears instead of web-page where you wanted to go. This ad is displayed for some time (15-30 seconds) and then you are allowed to go where you wanted to go.

This test imitates the case when Interstitial ad is activated with the help of address modification right after a mouse click.
When you click this link, you should be forwarded to a "good" information page info2.htm.
However, there is a Java-script installed, that redirects you to an Interstitial ad page when you click the link.

If, after clicking, you got to Interstitial ad page, your ad blocker is not capable of handling Interstitial ads. If, however, you got directly to a good page - WOW! - your ad blocker can bypass Interstitial ads.