The recent posting "Rethinking CSS Image Replacement" generated some pretty good discussion and got me thinking deeper about this issue. As a quick review, CSS image replacement is a technique of replacing a text page element with an image. An example of this would be including a logo on a page. You may want to use a «h1» tag and text for this for the accessibility and SEO benefits, but ideally you'd like to show your logo, not text.
Read More at : http://css-tricks.com/css-image-replacement/