It is important to follow recommended guidelines on web standards for various reasons...

1. To ensure cross-browser compatibility.
Your website should render correctly in all standards-compliant web-browsers.

2. To improve accessibility for people with disabilities.
The British Disability Discrimination Act makes it unlawful to discriminate against a disabled person by refusing to provide any service provided to members of the public - including websites.

Some other very important benefits include

• Easier manageability
• Reduced costs
  • Lower maintenance costs
  • Lower bandwidth consumption
    
• Compatability
  • Forward compatibility
  • Compatible with new browsers
  • Compatible with mobile devices
  • Compatible with text browsers and screen readers
    
• Extensibility
• More traffic
  • Better search engine visibility
  • Faster page load times