Pseudo-class :framed for the body element

I was thinking. Would it be useful if one could style a page differently if it is inside a frame?
body{background-color:blue;}
body:framed{background-color:green;}

Also I was wondering for the :checked pseudo-class. Wouldn't it be more useful if one could use it for all elements?
a{background-color:blue;}
a:checked{background-color:green;}

Regards, Martijn