Guideline 3. Use markup and style sheets and do so
properly.
When markup is used incorrectly, like using a table for
layout, it makes it different for users with special
software to understand how a page is organized, much less
navigate through it. Also don't use presentation markup
to structure the page, because it interferes with other
devices used by those with accessibility issues. Just
make sure to use CSS for structure and markup the rest of
the page according to specifications. If there is a
certain look that you can't seem to make work using
proper markup, you may need to consider if it is an
element worth keeping. Conversely don't be a developer
that abandons every design idea that seems difficult
using proper markup, it's a balance between the two
extremes.
3.1 When an appropriate markup language exists, use markup
rather than images to convey information. For example, use
MathML to mark up mathematical equations, and style sheets
to format text and control layout. Also, avoid using images
to represent text -- use text and style sheets
instead.
3.2 Create documents that validate to published formal
grammars. For example, include a document type declaration
at the beginning of a document that refers to a published
DTD (e.g., the strict HTML 4.0 DTD).
3.3 Use style sheets to control layout and presentation.
For example, use the CSS 'font' property instead of the
HTML FONT element to control font styles.
3.4 Use relative rather than absolute units in markup
language attribute values and style sheet property values.
For example, in CSS, use 'em' or percentage lengths rather
than 'pt' or 'cm', which are absolute units. If absolute
units are used, validate that the rendered content is
usable.
3.5 Use header elements to convey document structure and
use them according to specification. For example, in HTML,
use H2 to indicate a subsection of H1. Do not use headers
for font effects.
3.6 Mark up lists and list items properly. For example, in
HTML, nest OL, UL, and DL lists properly.
3.7 Mark up quotations. Do not use quotation markup for
formatting effects such as indentation. For example, in
HTML, use the Q and BLOCKQUOTE elements to markup short and
longer quotations, respectively.
