Most Core Web Vitals problems on marketing sites trace back to the same handful of causes: unoptimized hero images, render-blocking fonts, and layout shift from ads or late-loading embeds.
We start with the Largest Contentful Paint element specifically — usually the hero image or headline — and make sure it's preloaded and served at the right size, not just compressed. Then we audit font loading strategy, since a flash of invisible text or late web font swap is an easy, often-missed INP and CLS contributor.
Only after those are fixed do we look at third-party scripts, which are the most common cause of layout shift and blocking main-thread work on sites that otherwise look clean in a quick Lighthouse pass.