Writing web pages – the alt attribute is important.
There’s a nice article about writing for the web on A List Apart, with this anecdote about including alt attributes to provide content for visually impaired users:
“If a user is blind,” I reasoned, “what does he care that I have a photograph of the university tower on my website?”
My fellow designer shrugged. “Well, I guess if you don’t really care about what the image says,” she said slowly, “you really don’t need it in the first place.”
I’m generally pretty good at including useful alt text, but this is a great way of saying why we should do it…