2.1.74 [CSS-Level2-2009] Section 12.2, The 'content' property


The specification states:

 Value:                 normal | none | [ <string> | <uri> | <counter> | 
 attr(<identifier>) | open-quote | close-quote | no-open-quote | no-close-quote ]+ | 
 Initial:               normal
 Applies to:            :before and :after pseudo-elements
 Inherited:             no
 Percentages:           N/A
 Media:                 all
 Computed value:        On elements, always computes to 'normal'. On :before and 
 :after, if 'normal' is specified, computes to 'none'. Otherwise, for URI values, 
 the absolute URI; for attr() values, the resulting string; for other keywords, as 

Quirks Mode and IE7 Mode (All Versions)

The :before and :after pseudo-elements are not supported.

IE8 Mode (All Versions)

Dynamic updates to generated content do not update styles that are applied to generated content.