For example, the P element represents a paragraph while the EM element gives emphasized content. Elements cannot overlap each other. If the start tag for an EM element appears within a P , the EM 's end tag must also appear within the same P element. Some elements allow the start or end tag to be omitted.
Some elements have no end tag because they have no content.
These elements, such as the BR element for line breaks, are represented only by a start tag and are said to be empty . Attributes An element's attributes define various properties for the element. The attribute value is delimited by single or double quotes. Special Characters Certain characters in HTML are reserved for use as markup and must be escaped to appear literally. Other entities exist for special characters that cannot easily be entered with some keyboards.