4.10 [CSS-Level1-2008] Appendix B, CSS1 grammar
V0913:
The [CSS-Level1-2008] specification, Appendix B, states:
-
nmchar [-a-z0-9]|{latin1}|{escape} name {nmchar}+ "."{name} {BEGIN(AFTER_IDENT); return CLASS;}
Quirks Mode (All Versions)
Class names that begin with an unescaped digit are allowed in all cases, even if it is a known dimension.
Note In [CSS-Level1-2008], a class
name could start with a digit (for example, .55ft
),
unless it was a dimension (.55in
). In [CSS-Level2-2009],
such classes are parsed as unknown dimensions (to allow for future additions of
new units). To make .55ft
a valid class,
[CSS-Level2-2009] requires the first digit to be escaped (for example, .\\35 5ft
).
V0914:
IE7 Mode, IE8 Mode, and IE9 Mode (All Versions)
Class names that begin with an unescaped digit are not allowed in any case.