So, I'm checking out CSS Zen Garden – I'm now using firefox because of all the cool extensions it has specifically the PNH Toolbar which lets outlines the blocks (ie. grids) on the page, as well as this one: Edit CSS which lets you see and EDIT the current page's CSS and redisplays your changes in real time. (mentioned in the comments of this post, by Andrew Dupont) (THANK YOU for those!!!)
In doing so, I was examining the first Zen Garden page's CSS which uses this trick to swap images instead of text. That is just so cool. (I know, all you CSS-freaks have probably known about that little trick for eons.)