If you notice a drop in Tier1/G ad revenue, this could be due to a number of reasons. This usually indicates either a shift in traffic quality, or that our advertisers have reduced their campaign bids on one or more of your domain name keywords.
Tier1/G keyword settings can be manually optimized using the Master Keywords and Related Search Terms settings via the Manage Domains page.
Please note that Tier1/G ad revenue may fluctuate monthly, seasonally, etc., but revenue should stabilize over time.