The purpose of a web site is to communicate with one's visitors. So the primary goal of a web site should be to make this communication easy. Unless you are careful, you'll shut out up to a quarter of potential visitors. To make your site inclusive, you need:
- pages that load quickly
- roughly half the world is still on dial up
- requirements for javascript and flash minimized
- only a few graphics and of small file size
- pages that are accessible to any browser
- 20% do not use Internet Explorer
- pages that are accessible to any screen resolution
- 20% of the population uses resolutions less than 1024x768
- people should be able to enlarge or reduce font size for comfort
- pages with consistent look and navigation
- the pages should have a common visual theme so the site is clearly branded
- navigation placed in a consistent location
- links clearly identified
None of this is new or revolutionary. It's just that a large part of the web-design population doesn't follow these simple guidelines. Either they don't know any better, or else they think making web pages is an art project not a communications project.