Tab stops and indents as used in word processors are unknown in HTML. You should thus always avoid using tab stops in any topics intended for output to HTML-based formats, i.e. HTML Help, WebHelp and Windows Exe and ePUB eBooks.
Attempts to use spaces to create indented effects in HTML-based output will also not be very successful. This is because all HTML browsers ignore multiple spaces: It doesn't matter whether you enter a single space or 100 spaces, the browser will always render them as a single space – unless you enter hard (non-breaking) spaces with Alt+0160 on the numeric keypad.
Help+Manual actually converts multiple spaces you enter in the editor to space/hard space pairs in HTML output to get around this problem, but this still doesn't make spaces a good tool for indents – spaces render with different widths in different fonts and hard and soft spaces can also have different widths.
In the Tab Stops settings of the Paragraph formatting dialog you will see the following warning:
This might make you think that you can't use indents at all for HTML-based output but this is not the case. You can use indented paragraphs, you just shouldn't try to use tabs or spaces to make indents. You should always use Help+Manual's paragraph indenting functions.
How Help+Manual handles indented paragraphs depends on how they are formatted. Paragraphs with simple indents are formatted with margin settings.
Hanging indents are converted to tables, because this is the only way to make this construction stable in HTML.
Hanging indents are the only place you should use a tab stop. Here the tab character is used to insert the space between the text in the left part of the indent (the hanging part) from the main body of the paragraph, as shown in the example below. Paragraphs like this are converted to tables in HTML, which is the only really stable structure for displaying paragraphs with hanging indents in all browsers and the Microsoft HTML Help viewer.
This also works if the beginning of the first line is indented from the left margin. This will also be converted to a table structure that will be stable in HTML-based output.