Links and hot spots are created within your source document by formatting them with character styles using Doc-To-Help Markup Language (D2HML). Using Doc-To-Help's wide variety of predefined D2HML styles is the recommended way to create links and hot spots, but, if necessary, you also have the more advanced option of creating your own character styles for D2HML. There are also alternative ways to create links; these will be discussed later in this section.
In order for a hot spot in your source document to work correctly in the help target, it must have a corresponding character style with an active behavior in the Doc-to-Help project. The Behavior property of the style tells the hot spot what to do. For example, C1H Jump is a predefined character style in Doc-to-Help. The Behavior property of C1H Jump is Topic Link, so Doc-To-Help knows to treat the hot spot formatted with the C1H Jump style as a link to the topic.
A style is considered active when its Behavior property is set to a value other than None.
More:
Creating a Jump to a Topic in Another Document
Creating Keyword Links (KLinks)
Creating Mid-Topic Jumps Using D2HML
Expanding, Dropdown and Popup Text
Creating Active Character Styles
Alternative Options for Creating Links and Hot Spots in Word