The 7 mistakes that turn a website redesign into a legal and financial nightmare

Author: Boisdur-Salbris Matthieu

A redesign is not only about design. The real risk is breaking what already worked: SEO, high-performing pages, forms, legal compliance and the conversion journey. Without preparation, a brand-new site can take months to recover its rankings while competitors capture the visitors you spent years earning. A clear migration checklist protects both rankings and revenue. Here are the seven most common mistakes, and how to avoid them.

1) Forgetting 301 redirects

If your old URLs disappear without redirects, Google and users land on 404 pages: the rankings you built up slowly collapse and the user experience suffers. Before touching the structure, build a complete redirect plan (a URL map) that matches each old address to its new page, ideally with a 301 to pass ranking signals. Keep that map for several months after launch and monitor 404 errors in Search Console.

2) Not mapping backlinks

Inbound links matter: they pass authority and drive qualified traffic. If the target pages change without a plan, you lose that SEO value and visitors arrive on dead pages. List your backlinks (via Search Console or a dedicated tool) and redirect every linked URL to its closest equivalent, while strengthening internal links to the new pages.

3) Removing pages that converted

Many teams delete "old" pages that were still generating qualified leads. Before removing anything, audit your pages against your analytics data: traffic, conversion rate and the keywords they rank for. Keep the pages that perform, improve them instead of erasing them, and only retire the rest once a redirect is in place.

4) Ignoring legal compliance

Cookies, legal notices, terms and conditions, privacy policy: a redesign is the right time to bring everything up to date, because a new site must comply with the GDPR and its disclosure obligations. A broken consent banner, outdated legal notices or a missing privacy policy expose you to penalties and undermine visitor trust. Have every legal page reviewed before launch and make sure cookie consent is actually collected.

5) Breaking forms and analytics events

A redesign without tracking planning leaves you blind on real performance: you no longer know which pages convert or where your leads come from. Every form, call-to-action button and funnel step should be covered by a GA4 event and tied to a conversion goal, with the data verified end to end. Write the tracking plan before development and test each event in QA.

6) Hurting mobile performance

A nicer but heavier site can reduce both SEO traffic and conversions, because Core Web Vitals affect rankings and how quickly mobile visitors give up. Optimise image and video weight (modern formats, correctly sized assets), enable lazy loading and test your pages on slow connections. Validate LCP, CLS and INP before launch rather than after; a fast, well-compressed mobile experience keeps visitors browsing instead of bouncing.

7) Launching without a proper QA phase

Pre-production, a QA checklist and a rollback plan help avoid last-minute crises that cost traffic and sales. Test the key journeys (forms, checkout, mobile navigation, redirects) on a real staging environment before going live. Always keep a documented rollback procedure so you can restore the previous version if something breaks.

Conclusion: a successful redesign is a migration project, not just a visual refresh.