CLS is Cumulative Layout Shift, a metric for visual stability and unexpected layout movement.
It matters because technical issues can prevent great content from being discovered, rendered, indexed, or trusted. Strong technical foundations protect rankings during redesigns, migrations, content expansion, and platform changes.
Example
Example: If a review widget loads late and pushes the CTA button down the page, CLS increases. Reserving space for dynamic elements can prevent frustrating layout jumps.