We still hear the same opener in client calls: "Could this be our CSS?" Sometimes yes. Often no. On plenty of sites, the first real bottleneck is not your h1 style or a spacing token. It is third-party JavaScript that arrives early, executes long, and competes with the content users came for. Before we touch CSS on a slow page, we run one quick triage pass. It is not fancy. For a key template, this is a short set of script patterns we can usually spot in under an hour, then turn into action items with owners. If you want the full deep dive specifically on third-party offenders, read our Watcher guide on Third-Party Scripts and Performance: How to Identify and Fix the Worst Offenders . And if your biggest LCP element is an image (which it often is), see also our Image Optimisation Strategies for Better LCP Scores Below is the field checklist we use before opening a CSS file. It matters most when you manage multiple sites and regressions hide between client handoffs.…