Based on the search results, here are the most common web design mistakes that negatively impact SEO:

Poor Mobile Optimisation

Failing to optimise websites for mobile devices is a critical mistake. With the majority of users accessing the web via smartphones, Google prioritises mobile-friendly sites in rankings. Not implementing responsive design can lead to poor user experience on mobile devices, resulting in higher bounce rates and lower search rankings.

Slow Page Speed

Slow-loading websites negatively impact user experience and SEO performance. Google considers page speed as a ranking factor, and slow sites often lead to higher bounce rates.

Overcrowded Design

Too many elements on a page, especially on mobile, can harm user experience and SEO. Cluttered designs make it difficult for users to find relevant information quickly, leading to poor engagement metrics.

Thin Content

Pages with low word counts or inadequate content can negatively impact SEO. Thin content often results in short time-on-page durations and high bounce rates, signalling to search engines that the page fails to satisfy user intent.

Poor URL and Page Naming

Ineffective naming of pages, URLs, and images without considering relevant keywords can hurt SEO. It’s important to create descriptive, keyword-rich names that reflect page content and help search engines understand the context.

Lack of On-Page Optimisation

Failing to optimise on-page elements such as title tags, meta descriptions, and header tags can significantly impact SEO performance.

Blocking Search Engine Indexing

Some websites mistakenly block search engines from indexing their mobile pages, which prevents mobile users from finding their content in search results.

Ignoring Accessibility

Not considering accessibility features in web design can harm both user experience and SEO, as search engines favour sites that cater to all users.

By avoiding these common mistakes and focusing on creating user-friendly, optimised websites, businesses can improve their SEO performance and provide a better experience for their visitors.