Developers avoid mixing code by storing HTML and CSS code in separate files (HTML files contain only HTML code, and CSS files contain only CSS code).
You can create a CSS file by using the .css file name extension, like so: style.css
With a CSS file, you can write all the CSS code needed to style a page without sacrificing the readability and maintainability of your HTML file.
Take a look at index.html. Cut the CSS code in between the opening and closing
<style> tags and paste it directly in the new file called style.css.
Make sure to delete the remaining
<style> element (now empty) from index.html.