The HTML specification does not allow use of a number in a class or id, it is suggested that you preceed a leading number with an underscore (_). Windows IE does not obey the rules set for a class or id beginning with an underscore.
Test page Workaround is not included
Reported by: Aaron Gustafson.
Explorer 5-6 Windows | Reported on 14 February 2005.
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1 Posted by Áron Szigetvári on 5 October 2006 | Permalink
The specifications ( http://www.w3.org/TR/REC-html40/types.html#type-name ) say that "ID and NAME tokens must begin with a letter ([A-Za-z])"
It seems that the behaviour of IE is the right behaviour.