To improve SEO and eliminate duplicate content, it is essential to ensure that the text and HTML within your website are unique. This involves reviewing all pages and content for similarities. Duplicate content can negatively impact search engine rankings. To address this, you can rewrite content to express the same information in different words and sentence structures. It is also important to review and consolidate similar pages to avoid redundancy. Removing class and CSS styles from your HTML will not directly address duplicate content; the focus should be on the actual text and semantic structure.