What is the correct HTML for referring to an external style sheet stored in a subfolder called css?

The correct HTML for referring to an external style sheet stored in a subfolder called "css" is valid because it uses the appropriate <link> tag with correct attributes. The rel attribute is specified as "stylesheet," which correctly indicates the relationship of the linked document to the current document—it identifies the file as a stylesheet. The href attribute points to "css/mystyle.css," which accurately reflects the subfolder structure and the name of the stylesheet file.

Using the <link> tag in this way is standard and required for linking external CSS files in HTML, ensuring that the styles defined in the CSS file are applied to the HTML document. This method is critical in separating content from design, allowing for a more maintainable and organized web development process.