Text in each topic can contain limited formatting, including bold text, italics, and colors. Superscript and subscript are not allowed. Jumps between topics in the same Help file usually appear in the source document as double-underlined text (green by default, though this can be overridden) followed by a topic ID in hidden text. Popup links appear in the source document as text with a single underline (also green by default) followed by a topic ID in hidden text. (In the .hlp file, the jumps show up as green text with a single underline, and popups show up as green text with a dotted underline.)