This links to section 24 of the official HTML 4 specification of the official 252 allowed entities in HTML 4 and XHTML 1.0. However, you'll probably find the list prepared by Elizabeth Castro more useful!
Using HTML entities is the right way to ensure all the characters on your page are validated. However, often finding the right entity code requires scanning through 250 rows of characters. This lookup allows you to quickly find the entity based on how it