IDs vs. Classes
> Also, the spec explicitly states that a simple selector can have only
> 1 class (in section 1.4), but I could find no such limit on the number of
> IDs per simple selector.
> Is that a purposeful omission (and simple selectors can have multiple
> IDs) or does the same limit apply to IDs (only 1 per simple selector)?
The specific limitation for class values is there since the Cougar DTD
 suggests that the CLASS attribute value is a comma-separeated list
of values. CSS1 does not support this, and that's why we needed a
specific limitation. We're still debating if having more than one
class value makes sense. Feedback welcome.
For ID, noone have suggested it being more that an single value --
indeed, such a suggestion would defeat the purpose of ID. A
selector with more than one ID value would never select anything.
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