General Principles Navigation should be easy. A site map is helpful. Use graphics, images, and pictures to break up text, while bearing in mind that graphics and tables may take a long time to download. Very large graphics make pages harder to read.

Geenral Principles Offer alternate download pages in a text reader friendly style. Where possible design web pages which can be downloaded and read off-line. Moving text creates problems for people with visual difficulties. Text reading software is unable to read moving text.

General Principles Contents links should show which pages have been accessed. Most users prefer dark print on a pale background. Colour preferences vary.

Colours Some websites offer a choice of background colours. Encourage the use of hyperlinks at the end of sentences. Avoid green and red/pink as these are difficult for colour-blind individuals. Make sure that it is possible for users to set their own choice of font style and size, background and print colours.

Scotopic Sensitivity Syndrome The scotopic sensitivity syndrome - proposed by Helen Irlen - is that there is an array of perceptual anomalies that allegedly cause visual dyslexia, (Pumfrey and Reason, 1991). The syndrome allegedly consists of visual distortions in four categories. Light sensitivity : the ability to accommodate high contrast and glare. Visual resolution: the ability to see print clearly and without distortions. Span of focus: the ability to perceive groups of words at the same time. Sustained focus: the ability to do with tasks with the eyes in a relaxed state with the objects in focus

Population Claims have been made that between 50 and 75 percent of learning disabled people suffer from this syndrome" Pumfrey and Reason (1991). However, a significant proportion of the 'normal' population also suffer from this syndrome (Brown pers. com. After attending an Irlen presentation). Pumfrey and Reason (1991) reviewed the literature on the use of lenses and filters, they consider that the evidence "indicates that visual problems do not seem to be a major cause of dyslexia". Dyslexic child suffering from scotopic sensitivity are bound to have their problems exacerbated. Although the Irlen lenses involve over 140 variations "the most significant effect of Irlen lenses is to reduce light overall rather than affect specific colours" (Moseley (1990b) cited by Pumfrey and Reason, 1991).

Remedies Should teachers suspect that a child has scotopic sensitivity the most immediate response would be to reduce the light intensity. Certain blackboards and whiteboards are renowned for giving off a glare when viewed at certain angles. Moving the child to a different part of the classroom may well help. The printed word may be modified by overlaying sheets of coloured acetate such as are used for OHP transparencies. These are available in a variety of colours and intensities. Photocopying material onto coloured paper is another means of avoiding the complications of scotopic sensitivity. It is unlikely that many schools will be able to print specialist handwriting paper in unobtrusive shades as reported by Brown (1990

Background Colour On Computer Applications change the background colour On the web this can be done using CSS or it can be done by setting browser options