"illegal" entities for HTML

Ladies and Gentlemen,

Can you please tell me why the following entities are considered illegal
‘	(left single quotation mark)
’	(right single quotation mark)
“	(left double quotation mark)
’	(right double quotation mark)
–	(en dash)
—	(em dash)

All of them works excellenly with MSIE and NN, both on PC and Mac
platforms

Best regards

Eugene Poliakov

Received on Thursday, 9 July 1998 22:45:46 UTC