class / ident / numbers

Hi,

The CSS3 Selectors test cases state that this is not a valid class 
selector:

.\5cm { ... }

However "\5cm" seems to be a valid identifier, according to the definition
of the CSS syntax, as it begins with an escaped char. There doesn't appear
to be anything in the spec saying that class cannot begin with a digit. 
What have I overlooked?

Michael Day

YesLogic Pty. Ltd.