Why might I encounter a 'Cannot find module '@ tailwindcss/postcss' error?

This error typically indicates that the `@tailwindcss/postcss7-compat` (or `@tailwindcss/postcss8`) package, or a dependency of it, is not installed or is not correctly linked in your project. It's common when setting up Tailwind CSS for the first time or after updating dependencies. Ensure you've run `npm install -D @tailwindcss/postcss7-compat` (or the appropriate version for your PostCSS version) and that your `postcss.config.js` file is configured correctly.