Designing Web Pages for Blind and Visually Impaired.
The following information is intended to provide some basic information on how to design for the visually impaired. It is not seen as being comprehensive but instead is more to raise awareness of the issues involved. There are many very useful web sites that go into far more detail and also give useful addresses where you can check your site for accessibility.

Site design:

* Use a standard page layout throughout the site.
* Use navigation structure that is clear and consistent.
* Offer navigation bars.
* Provide a description of the site layout and how to navigate it.
* Offer a site map such as a clear navigation bar.
* Be sure everything can be operated from a keyboard.

General:

* Layout uncluttered screens.
* Leave considerable space around all items.
* Avoid tiled backgrounds, because text can become obscured.
* High contrast between text and background is important in choosing colors.  A simple test is to print it in black and white.
* Avoid dark or bright colored backgrounds.
* "Front load" information at the beginning of paragraphs, lists, headings, etc.
* End all sentences, headers, list items, etc. with a period or other suitable punctuation. It will help screen readers interpret lists.
* Use the full text of a date: February 28, 1996.  The 00/00/00 format is subject to misinterpretation.
* Do not use emoticons (those smiley faces) or other drawings done with ASCII text symbols.
* Use vertical lists of hyper links, not several on the same line.
* The text of each link should be brief, yet make sense when read out of context.

HTML:

* Font style and size sshould be consistent; avoid drastic contrasts.
* Avoid blinking text.
* Avoid "marquee" effect.
* Nest headings properly; do not use them for formatting layout.
* "List elements" should be used to create lists, not to indent text.
* Do not use tables to arrange text documents in columns or for page layout.
* Provide titles for horizontal rules, acronyms, and abbreviations.

Advanced HTML:

* Use alternative text, alt tags, for all graphics, images and image maps.
* Graphics, such as tables, that present important information need an associated longer description of the graphic.
* Table cells should be explicitly associated with row and column labels.
* Image maps should be accessible and keyboard navigable.
* Applets and scripts that convey information need alternative presentations of content.
* Supplement audio information with a transcript.
* Frames must have titles.
* User input forms should not have image maps for graphical "submit" buttons.
* Provide email, fax and telephone addresses for questions about any graphics, forms, applets or other special presentations that may be unclear.

Designing to meet the needs of visually impaired people

1 Typeface
The choice of typeface is less important than contrast, type size, weight and the spacing of characters.

Quirky, unusual, script and tilting faces are obviously highly inappropriate for legible continuous text.

There is no valid research to support the preference for a sans serif typeface (such as Arial or Helvetica) over a seriffed one (such as Times or Century). Seriffed faces are more 'readable' in continuous text for regular reading. This may equally apply to large print texts.

Some institutions such as the Partially Sighted Society strongly recommend the use of a sans serif typeface such as Helvetica when producing documents for the partially sighted. 'Helvetica bold' was adopted widely as the result of some testing carried out in the 1970s.

Now we have the results of more recent investigations alongside a much wider range of typefaces to choose from. We suggest avoiding very light-appearing weights of fonts.

2 Type size

For the partially sighted 14pt type (average x-height of 2.5mm) is suggested as a minimum by RNIB. Sometimes 16pt may be needed by some visually impaired readers. There is no benefit from using a type size larger than 20pt.

These recommendations obviously depend upon the typeface and weight used. For the general reader type sizes between 8 and 10pt are frequently used. The RNIB aims to set all its texts for usual readers in 12pt.

Remember that different types with the same 'point size' have different appearing sizes. The effective size of a typeface is actually related to the height of the lowercase x:



3 Type weight

The tendency has been for setting text in bold because of its contrast on a white page. However, more recent findings suggest that a medium weight or semi-bold may be more legible. The RNIB's See it right was set in New Baskerville semi-bold.

4 Italic

Traditional italic type should clearly not be used for continuous text for any group of readers. As a means of emphasising important words or phrases it may be appropriate. This is particularly important if body text is in a semi-bold; the use of bold for emphasis may not be enough. Titles of books etc. should be italicised as in text for general readers.

Remember that the italic versions of most seriffed fonts are very different from their roman equivalents - some would be tough going for visually-impaired readers. 'Italic' versions of sans-serif fonts are normally just sloped versions of the roman and should not have the same potential problems:



5 Capital letters

Text in all-capitals is much harder to read than normal-case continuous text. However, one or two words set in capitals do not create reading problems. Because they are bigger, capital letters are easier to see than lower-case letters, so may be suitable for labels.

6 Numerals

It is important that numbers are as distinct as possible. This is particularly vital for documents such as bills, bank statements, and accounts. Some typefaces have figures that are easily misread: 3,5 and 8, as well as 0 and 6 can be easily confused.

Also the figure one '1' can be confused with I, and l and even ! A 'hooked' number one is much more distinctive than a straight vertical stroke '1'. Choose a typeface with distinctive numbers. The RNIB publication See it right had its New Baskerville figures redrawn to improve readability and help increase the distinction between different figures.

7 Interlinear space

Leave reasonable space between lines of type. RNIB suggests interlinear space should be at least +2pt for type sizes between 14pt and 20pt eg. 14pt type with 16pt leading. This of course depends on line length and on the x-height of the type you are using. Lighthouse recommends adding 25 to 30 per cent of the text point size between lines. We're with Lighthouse on this one. Text set in longer lines needs more interlinear space than text set with a narrow measure (see 8).

8 Line length

This should ideally be in the range of 50-65 characters. Some visually impaired people may prefer even shorter lines than this.

9 Line endings

Avoid splitting words at the ends of lines. Switch hyphenation off.

10 Setting mode

Use unjustified, ragged right, text setting with even word spacing. Do not justify text: this creates uneven word spaces and makes the text harder to read. This appears to reflect  research among regular readers which suggests that unjustified text is easier to read at the margins of reading ability - with beginning readers and in poor light.

11 Word spacing

Always use even word spacing. In some documents for the visually impaired there has been a tradition to use double word spacing. This has not been fully researched. While it may help some readers, others may find double word spacing actually hinders reading.

12 Paragraphs

Leave space between paragraphs. There should be more space between paragraphs than between lines. Other ways of setting paragraphs such as indenting the first line, out-denting the first line, using a bullet or asterisk, make text less easy to read for visually-impaired readers.

13 Headings

Headings should be clearly differentiated from the main text using some combination of size, weight and space. Capitals should not be used for headings, nor should out-denting. A second typeface such as a sans serif in contrast to a serif body text could be used, but no research has been carried out to prove its effectiveness. Headings in bold are clear as long as there is plenty of contrast between the weight of the heading and that of the text.

Headings seem easiest to read when ranged left with the text. It has not been established whether centred headings are harder to read than ranged left ones, though common sense suggests that they are.

Extra space around headings may be enough to differentiate them from main text.

In the past, documents for visually impaired readers often used underlined headings. There is no conclusive evidence that this assists readability.

14 Design and layout

Layouts should be simple and clear with recognisable patterns for levels of heading, numbering systems, and treatment of specific information. Generous margins for pages of text help reading: don't lead the eye off the page.

If text is set in columns make sure the space between columns is generous. If space is limited, use a vertical rule. It is helpful to provide 'navigational aids' for the reader such as a contents list for multi-page documents, and rules to separate unrelated sections. Bullets can assist the structuring of lists.

15 Forms

On forms, visually impaired people often need generous space to fill in hand-written details. Their hand-writing tends to be larger than average, and visual impairment, particularly in older people, is often accompanied by other physical problems which make it hard to write neatly. This means they need more widely spaced lines or larger boxes to fill in than those on conventional forms. This also applies to tick boxes, which should be about 50% larger than their standard size.

With Thanks to the following sites for the above information.

Internet Accessability- Web Page Design
http://www.scils.rutgers.edu/~mowalker/access05.htm

HTML Validation Service
http://validator.w3.org/

Web Server for the Visually Handicapped
http://www.dpa.org.sg/VH/

Designing to meet the needs of visually handicapped people
http://www.textmatters.com/guides/visually_impaired.html

Royal National Institute for the Blind
http://www.rnib.org.uk/

Lighthouse Incorporated
http://www.lighthouse.org/

Websight Project
http://www.nottsrcc.org.uk/websight/