A style defined in an (X)HTML tag takes priority over styles defined in the head of the (X)HTML document. Styles defined in the head of the (X)HTML document take priority over styles defined in an external style sheet.
For example if you have the font colour of text contained within a <p> tag black in the main external style-sheet of your website but on one page you wish to have it dark grey. You don’t need to add a new class and give it to every <p> tag to do this, you can just define a fresh style in the header of the document to change the font colour which will take priority over the original style.
