Different browsers support a wide range of features and accessibility options.
However, many users aren't free to choose, so you should not assume your readers have access to the latest technology. The bottom line is you have to prepare for the worst browsers. When a page can't be made accessible without compromising its usability or appeal, you often need to provide an alternate page that is less appealing but more accessible. For an example of alternative pages, see the universal version of this site. All rights reserved.