paragraph, i.e. to justify a single p element using CSS, you could embed the declaration directly into HTML, writing
in HTML) and using a selector based on that (writing e.g. p.special {text-align:justify;} in a style sheet in a separate CSS file linked to the document or inside a style element in the document). This paragraph has such a declaration associated with it (using the latter technique, but that is irrelevant, or at least should be, by the specifications), so it will demonstrate how your browser treats the CSS way of justifying a paragraph.