CSS (Cascading Style Sheets) help to make your site pretty. A developer or designer can adjust the fonts, spacing, coloring, and flow of text without a lot of advanced programming. The latest CSS, CSS3, also helps with enhanced navigational menus, such as a sub menu or a mega menu, which allow visitors to glance at descriptions upon hover. Additionally, CSS3 helps with responsive designs for mobile and tablet compatibility.
The latest HTML, HTML5 is outstanding universal code that makes it easy to include and handle audio, video, multimedia and graphical content on the web in multiple browsers, and also assists with responsive design. Additionally, HTML5 makes your site load faster.
Web developers who know code can customize WP Plugins, forms, and other stand-alone interactive elements for your site, without interfering with core WP source code.