It seems the validator does not recognise the "inherit" value for the shorthand font property.

eg, for

p,h1,h2,h6 {
    font:normal normal normal 0.8em/1.3em inherit;

I get the error:

Invalid number : font Too many values or values are not recognized : normal normal normal 0.8em/1.3em inherit

Note:  I define the font-family earlier:

body {
    font-family:"Swis721 Lt Bt","Trebuchet MS",sans-serif;
I have tried validating it in both CSS2.1 and CSS3.

Also:  I tried replacing 'inherit' with 'none' (which is not defined at all) and it passed.