Is the use of relative values in font sizing for accessibility still useful in general, or only for IE6?

All other browsers (not IE6) are scaling the size of the whole layout in px. So what's the purpose to use em and % if we are not thinking about I开发者_运维百科E6?

Have you considered all major mobile device (eg, phone) browsers as well?

If you specify font sizes by em, your codes will be more flexible and easier to maintain when you want to change the underlying font size later. Also, as Dan McG has said, not all browsers scale in pixels.

em and % help in making the dimensions independent of the device resolution by default

Even if all browsers did support scaling of whole layout as you describe, the user experience is not optimal if they have to scale the web page every time to suit their display's resolution.