Older readers may have reduced vision and require larger type with more separation between the background and the text. Type that is below 12 point may be used, but sparingly, and for readers over sixth grade and under 40 years of age. Avoid light or bright colors for text. Avoid complicated backgrounds. Ensure that great design and great content make a great product.
Time is limited.
Know your audience. This sounds so simple, but often we don't know what our audience wants or how they best receive the message. Be aware that reading skills influence design. Provide visual breaks and rest spots. Use color to categorize content.