the current templates/classic/html/style.css doesn't 
validate at http://jigsaw.w3.org/css-validator/. this is 
mostly due to missing length units on non-zero values 
(eg. padding: 1 0 0 1).

attached patch
* adds these missing length units (px)
* removes length units from zero values
* removes / merges redeclared selectors and elements 
with the the same declaration-blocks
* adds background-color: to selectors with color: ("good 
practice to avoid conflicts with user stylesheets")
* uses short rgb color notation (#444 instead of 
#444444) where applicable
* uses short values margins and paddings (margin: 0 
instead of margin: 0 0 0 0) where applicable

and makes the file validate. it applies with patch -p0 in 
templates/classic/html. a similar fix should be applied to 
the 'minimal' stylesheet.