in Google adsense, if a user from any territory revisits page impression is getting updated but that eCPM is not getting updated its showing zero only, does it work only for unique visitors?
The "eCPM" is "Effective Cost per Mille" or the cost per 1,000 impressions. So if you had 2,000 visitors and earned $2, your eCPM would be $1.
Unique visitors are not counted, only raw page views. But if eCPM is showing as zero, it means either you are not earning anything (no one clicked on the advert) or simply there is not enough data to calculate it accurately.