Make your website functions accessible to as many people (and quite possibly, search engine robots) as possible. Consider the following principles:
Perceptibility – when everyone can perceive your website’s design, regardless of their sensory abilities. Remember, there may be people who are deaf, blind, or colour blind that may visit your website. Use ALT tags for any images on your website that provide a good description ofwhat the image is.
Simplicity – where everyone can understand how your website operates, and how to find information, and navigate through your website pages, regardless of their experience, literacy, or concentrarion level. Create a Sitemap before you attempt to write a single line of code!
Forgiveness – help visitors when they make an error using your website. This might be an automated response, or alternatively, a manual response where you contact them directly.
Operability – where you design your website so everyone can use it, regardless of their physical abilities.
The World Wide Web Consortium maintain guidelines for website accessibility.