I don't recommend you to use this service. A lot of extra annoying pop-ups when you click on ad. Do we return to 2005 year? OMG!
Although you can consistently accumulate money for pop-under ads displayed on your websites/blogs, the earnings potential isn't much and you must accumulate 10 bucks in your account in order to cash out. More importantly, the ad experience is terrible in that if your visitors click anything on your site, an interstitial ad that appears from Pop Cash may make it too hard for them to return to your site without closing out all of the extra tabs/windows that pop up.