2.7 Indents, Tabs, Bullets, Paragraphs (hierarchy cues)

Typographic considerations for these elements are very important. Most website neglects these features, creating visual chaos. Look at any news, medical, encyclopaedic-related website’s homepage for examples.

The overall form of the page should be smooth and uninterrupted. There should not be too much modulation in the vertical alignment. Alignments are necessary to help the tracking movements of the eye. Too many indents can quickly confuse low-vision people. Maintaining vertical alignment and separating text blocks with line space is preferred.

Indenting and out-denting can be confusing for low-vision people (Text Matters). Indents are not necessary in paragraphs when there is ample line space between paragraphs. An additional line space is preferred for paragraphs. In print there is a tradition of indenting the first line of a new paragraph. A line space together with an indent is not necessary.

However, indents can be a useful in visually grouping like information. Tabular information should be formatted in a table. Listing grouped information with HTML list items can assist those with low-vision. Indents for blocks of related text should be large enough to signal their function to low-vision readers, but not overly large so that the connection between main text and secondary text is lost. For a 19 pixel font we recommend at least one and one-half em, but not more than two and one-half em of spacing.

Bullets and other hierarchy cues (including numbers) can be used to identify secondary texts. Care should be taken that there is enough contrast between the cues and the text. The cue should be at least as high as the x-height of the text, and of darkness equal or greater than that of the text. Out-dented bullets are preferred over indented ones especially when there are multiple lines per bulleted item. The space between bullet and text should be chosen so as to allow the eye to connect them. This distance should be between one em and one and one half em. A space above the bulleted item to separate it from the main text or a previous bulleted item is preferred.

Line space between bulleted items should be between 1 em and 1.3 em.  A clear vertical alignment of all related, bulleted text needs to be maintained. Limit the hierarchy to two levels as more than two levels will create difficulty for low-vision readers. (Strickler et al. [2002] found that subjects did not like too much variety in information hierarchy.  Scanning the page for new chunks was not preferred.)

For text blocks the setting of flush left, range right is best for reading. Centred alignments and flush right, range left settings creates irregular rag on the left margin; these alignments should be avoided. These alignments make it difficult for the eye to find the next line of text.