Certain special characters are represented in HTML by a name or a number, referred to as an entity. HTML includes entity names for characters such as the copyright symbol (©) the ampersand (&), and the registered-trademark symbol (®). Each entity has both a name (such as —) and a numeric equivalent (such as —).
Unfortunately, many browsers (especially older browsers, and browsers other than Navigator and Internet Explorer) don't properly display many of the named entities. Most browsers display most of the commonly used numeric entities, but remembering an entity's number is harder than remembering its name.
For a list of entity names and numbers, see the entities table.