# Blog

- [What is MER and how is it different from ROAS?](https://www.performetic.com/en/blog/what-is-mer-vs-roas): How to calculate marketing efficiency ratio (MER), why it gives different answers than ROAS, and which metric ecommerce brands should use for which decision, with worked examples.
- [How to handle out-of-stock and discontinued products for SEO](https://www.performetic.com/en/blog/out-of-stock-discontinued-products-seo): How to decide between keeping, redirecting or removing pages for temporarily out-of-stock, permanently discontinued and seasonal products.
- [How do trust signals affect ecommerce conversion?](https://www.performetic.com/en/blog/ecommerce-trust-signals): Security badges, return policies, contact details and transparent costs: which trust signals actually help a lesser-known brand win the sale?
- [Google Shopping vs Meta catalog ads: which should you use?](https://www.performetic.com/en/blog/google-shopping-vs-meta-catalog-ads): A side-by-side look at Google Shopping and Meta Advantage+ catalog ads: intent, audience, feed needs, creative, measurement and how to split budget between them.
- [How to use Demand Gen campaigns for ecommerce](https://www.performetic.com/en/blog/demand-gen-campaigns-ecommerce-guide): When and how to use Google's Demand Gen campaigns for an online store: placements, creative formats, product feeds, lookalike segments, bidding and budget guidance.
- [Why your Meta learning phase never ends, and the fix](https://www.performetic.com/en/blog/meta-learning-phase-learning-limited-fix): Why Meta ad sets get stuck in the learning phase, which edits reset learning, and how to fix a Learning limited status step by step.
- [Which KPIs should an ecommerce business track?](https://www.performetic.com/en/blog/ecommerce-kpis-to-track): The ecommerce KPIs worth tracking across acquisition, conversion, retention, profitability and operations, with formulas, data sources and review frequency.
- [Static image vs video ads: which works when?](https://www.performetic.com/en/blog/static-image-vs-video-ads): When static image ads win, when video wins, a decision table by product type and funnel stage, platform requirements and a test plan that compares formats fairly.
- [E-invoice and e-archive rules for ecommerce in Turkey](https://www.performetic.com/en/blog/e-invoice-e-archive-invoice-turkey-ecommerce): Thresholds, transition deadlines, the 2026 e-archive change and the mandatory fields on online sale invoices for brands selling online in Turkey, based on Tax Procedure General Communiqué No. 509.
- [How to use web push notifications for ecommerce](https://www.performetic.com/en/blog/web-push-notifications-for-ecommerce): What web push notifications are, when to ask for permission, how they work on iPhone and which ecommerce use cases actually drive sales, with tips to protect opt-in rates.
- [What is incrementality testing and how do you run it?](https://www.performetic.com/en/blog/incrementality-testing-guide): How to measure whether your ads really create extra sales using controlled tests, covering Meta and Google lift studies and geo tests with ecommerce examples.
- [Traffic dropped after a Google core update: what now?](https://www.performetic.com/en/blog/google-core-update-traffic-drop-recovery): A step-by-step guide to diagnosing an organic traffic drop after a core update, separating the real cause and building a durable recovery plan.