all: initial. This resets all CSS properties to their initial value, and undoes browser stylesheets – in this example, the
blockquote is no longer indented or
display:block; as you’d expect.
Other values for the property are
inherit, which changes all the properties applying to the element or the element’s parent to their parent value, and
unset which changes all the properties applying to the element or the element’s parent to their parent value if they are inheritable or to their initial value if not.
They’re supported in Opera, Firefox and Chrome. The Mozilla Developer Network page has good examples of these.
What’s curious, though, is that the value that would be the most useful isn’t there at all. I wouldn’t want to completely strip away User Agent styles and then have to reset elements to display block-level and then indent them in CSS. I wonder why there’s no
all: ua-default (or somesuch) to reset them to the User Agent style sheet default?
Update: Saperlipopette! There’s a very good French-language post La cascade CSS avancée: all, initial et unset for those who speak Oohlala.