CSS stands for Cascading Style Sheets. It controls the appearance of HTML elements of your store’s webpage, meaning helps to customize the appearance of your online store. It allows you to add your own CSS styles to overrule the default styles of your theme.
Here's how you can set up Advanced CSS for your Store
From the left panel in your dashboard select Online store -> Store Settings -> Edit Theme
The Customized URL format is more SEO friendly compared to the default product URL on the product page. Customize Url will change the URL format of the browser link on your product page.
Here's how you can Set Up Customized Url for your Products
From the left panel in your dashboard -> Online store -> Store -> Banner images -> Customize Url -> and ✓ on the URL Format
Checkbox Url format -> Click on a product link -> The Url format on the Product page browser appears in the following way
if Undo the checkbox Url format the Product Url Format looks the following way.