Benefits of Accessible, Standards-Based Pages
Immediate Benefits
Lower site development costs
Web standards sites are easier to produce, with far less time spent just getting them to work properly!
Longer-Term Benefits
Accessibility
An increase in accessibility means more people will see your site, and more people will find their visit a pleasant and productive experience. Importantly, websites are specifically mentioned in The Disability Discrimination Act Code of Practice, and it is therefore legally and ethically something that should not be ignored.
Search engine optimised
The first and most important step in SEO is a clean, semantic site. There is much more to SEO than this, of course, but a web standards-based site is the foundation for effective search engine exposure.
Far lower bandwith costs
Web standards sites are around 30% - 60% smaller than inefficient older-style ones. For a site with very many visitors this can lead to absolutely huge savings.
Easier maintenance
In the past, a website's code was often very much tied to a specific presentational structure; modern code allows layout changes, even complete design overhauls, with relative ease.
Because the code is clear and logical, developers working with it for the first time will find it easy to understand. Gone are the days of 'tag soup' that only the original developer could fathom!