You will most likely only need to access these advanced editing sections if you are working with a third party to design or market your website. If you're not sure about how to edit this content, do not make changes here! Edits to these sections may result in broken third party tools or a broken website template.
If you need to access the CSS (custom style sheet) or <head> content of your site, navigate first to Website >> Design:
Scroll to the bottom of the page to find the "Developer Tools" section:
Note: if you are looking to update the style of a certain page or an element on your website, we recommend working with our Customer Service team on those changes. You will likely need to make that update on the specific page, not here on these global tools.