Entity substitution solves various issues with web browsers and HTML. The HTML 4.0 standard provides definitions for some characters, such as the em dash (Unicode character 8212), and the publishing process will use this definition. However, some browsers may not fully support the HTML 4.0 standard, resulting in dropped or malformed characters. You can usually solve this by substituting a numeric character reference for the problem character.

The HTML Help navigation pane is a proprietary format that is not based on HTML. For example, if the em dash character (Unicode character 8212) was included in a title that displayed in the HTML Help navigation pane, it would not display properly because the navigation pane cannot display Unicode characters. In this example, you could substitute a hyphen character to achieve acceptable results.