MaxDesign has a tutorial on The benefits of Web Standards to your visitors, your clients and you:

2. What are Web Standards about? These 'Web Standards' are designed to:

deliver the greatest benefits to the greatest number of web users
ensure the long-term viability of any web document
simplify code and lower the cost of production
deliver sites that are accessible to more people and more types of Internet devices
continue to function correctly as browsers evolve, and as new devices come to market
For web designers and developers, Web Standards are about using standards (Structural, presentational, Object and Scripting languages) and best practices (valid, semantic and accessible code) to benefit your users, your clients and yourself.

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