Sure you can!
<img src="404" alt="Alt Text">
img {
color:green;
font:40px Impact;
}
I do this as a fallback for header logo images, I think some versions of IE will not abide. Edit: Or Chrome apparently - I don't even see alt text in the demo(?). Firefox works well however.
img {
color: green;
font: 40px Impact;
}
<img src="404" alt="Alt Text">