CSS or Cascading Style Sheets are designated as the web design standard for creating websites. The old practice of table-based layouts and HTML hacks create slower loading websites that have potential issues when viewed in more modern web browsers. One of the major issues is it hinders your position on search engines.
As written on the W3C website:
“The World Wide Web Consortium (W3C) is an international consortium where Member organizations, a full-time staff, and the public work together to develop Web standards. W3C’s mission is: To lead the World Wide Web to its full potential by developing protocols and guidelines that ensure long-term growth for the Web.”
The W3C provides validation tools to verify that your code is written correctly, both the XHTML and the CSS.
Advantages of using CSS and valid code include the following:
Your website can gain significantly better search engine results. This is accomplished through CSS positioning of elements to put the most important elements first. It also allows you to move most of your design elements off of your XHTML page and leave cleaner content for the search engines to index.
Your website will load faster. CSS takes those design elements off of your XHTML page and will replace those page-heavy tables to give you clean, fast-loading code. Fast-loading pages mean no losing visitors because they have to wait.
Your website will be compatible with newer browsers and will continue to be in the future. Since CSS is the web standard determined by the W3C it ensures that your site will continue to show properly as browsers are updated.
Your website can be created for multiple views. With CSS you can create pages to be viewed on desktops, tablets, and smartphones.
Your website design elements can be updated from a single file. The CSS document can be linked to all your website pages allowing you to change any design element and have all your connected pages updated simultaneously.
The advantages are significant and we re-design existing websites to meet the web standards with CSS.