Image replacement issue

I am confused by selecting the best technique for image replacement in web design.

Here at this weblog some techniques are provided:

http://css-tricks.com/css-image-replacement/

Which technique in image replacement is better?

Why should we use css image replacement开发者_C百科 when we can use 'alt' attribute of img tag to put some text ?

The alt attribute can't handle CSS. Image replacement displays a styled element instead of the image, which is good for image-less (if they exist) people.

As for the "best", I'd say No. 3 is good. No extra markup and no issues. All the other solutions suffer from one or the other.