specificity & user style sheets

body * {background:#000 !important; color:#fff !important;  
visibility:hidden;}
h3 *,img {visibility: visible;}

provides an interesting precis or transformation of for instance the  
BBC homepage: http://www.bbc.co.uk
however the use of h3 isn't consistent across even a few links let  
alone the BBC domain, or the wider web.

regards

Jonathan Chetwynd