Some of the major advantages of CSS are
• Creation of smaller file sizes
• Greater control over page structure
Smaller size files and CSS: you can reduce the overall code-amount present in your web pages. This is possible by taking out styles from an HTML page and putting it a standalone style sheet or .css file. Pages containing less code make for smaller file sizes that are preferred by all search engines. The SEO community generally considers page sizes up to 100KB as good.
Better control over page structuring: When using CSS, you can structure your pages as per HTML standards with no compromise on the appearance and feel of the a page. CSS caters to well-structured pages allowing designers to create pages that are attractive and have great flair.
It is best to use CSS in Website design and write one or more than one .css file to house all the style codes and then apply it to the relevant pages with the HTML link tag. Adopting this approach will allow everything related to the look of your web site to be found at a single location and not have it jumbled up with the site’s contents. This will allow you to change your site’s content without affecting its.