If you prefer videos to articles, there's an episode of HTTP 203 on this topic. Ok, on with the article… <img src="/c/silly-cat-0521eef9.jpg" alt="A black cat lying down, wearing a flip-flop on one foot. It's a human flip-flop so it doesn't fit. Regardless, the cat seems pleased with itself." />Good alt text means that screen reader users get the same 'meaning' from the page as a fully sighted use