CSS or Cascading Style Sheets are used for creating fast loading web pages and for minimising the coding efforts especially when the website is going to use the same style throughout the website. CSS also keeps the page uncluttered as designing and formatting codes are stored in a different file leaving only the site's content in the web page. When we use CSS, we can easily modify design of the entire site without having to make changes in every page.

CSS also has many SEO related benefits besides the above design related benefits. The first benefit is that the pages can be loaded faster. Search engines love pages that are light and fast loading. As all the codes are presented in a different file, the pages themselves become light making them SEO friendly. Moreover, we will also not have problem of duplication of content on each page pertaining to the navigational menu, which repeats itself in each page. Though search engines may not penalise you for duplication here, it may skip some of the pages as it finds the content to be redundant. Therefore, when we separate the content from the codes, each page will have fresh content without the codes on navigational menu repeating on each page.

Secondly, since all the codes are stored in a different file, the page is clean and the important content for which we would like to get listed can be moved to the top of the web page. Search engine spiders need not have to plough through hundreds of lines of codes before it finds the content of your website, which matter the most for the search engines. If the important content is going to be at the bottom of the page, it will not help you in getting good rankings in the search engines. CSS allows you to bring your important content to the top of the page. This will allow the spiders to crawl each page fully.

Thirdly, search engines are also able to crawl all the pages of your website because they can easily find the internal links, which will otherwise remain hidden within the codes.

Moreover, as CSS allows us to keep the codes separate from the content, we can easily try the performance of different texts and keyword structures without affecting the overall design of the website.