For any style sheet to affect the HTML document, it must be “glued” to the document. That is, the style sheet and the document must be combined so that they can work together to present the document. This can be done in any of four ways:
Apply the basic, document-wide style sheet for the document by using the STYLE element.
Apply a style sheet to an individual element using the STYLE attribute.
Link an external style sheet to the document using the LINK element.
Import a style sheet using the CSS @import notation.