To improve SEO and eliminate duplicate content, it is crucial to ensure that the text and HTML within your website are unique. This often involves rewriting content to express the same information in different ways, avoiding verbatim repetition. Removing class and CSS styles from your HTML will not directly impact duplicate content; however, it’s a separate best practice for improving website performance and maintainability. The focus should be on creating original, high-quality content that accurately reflects the information you’re presenting. Tools can help detect duplicate content, but ultimately, rewriting is the most effective solution.