Write - HOW-To: Convert PSD to HTML/CSS - page 92

Before you add the :before selector, set the thumbnail
paragraph to be relative positioned.
The p.thumbnail is set with a full height background
(gray) and a bottom padding property of 20 pixels
to pull that gray background more to the bottom, to
replicate it from Monoplate .
Using the :before selector you position a 24px tall of
white background on top of that background, but
because of the :before absolute position, the white
background gets priority and it would sit on top of
any content inside the li (e.g. including the thumbnail ).
To disable that, position the thumbnail itself on
top of the white background which is easy with a
position:relative and a z-index value of 1, as such:
#albums li p.thumbnail img {
position:relative;
z-index:1;
}