On 2 Oct 2013, at 10:43, Greg Gamble wrote:
OK, I'll bite :-)
What is origin, weight, and specificity? I hear the terms and I
think I get it ... but, to hear it from the Master would be great.
Well, the Master isn't available (something about a drum circle and
looking for a police box key), but I'll take a swing at it. The details
are here:
http://www.w3.org/TR/CSS2/cascade.html#cascade
Here's what I meant:
* Origin -- whether the rule comes from the author, the user, or the
user agent. There's a precedence order defined in the specification, so
that (for example) author rules always override user agent rules.
That's why you saying 'strong {font-weight: normal;}' removes the
boldface treatment even if there's a user agent rule that says something
like 'h1 strong {font-weight: bolder;}'.
* Weight -- called "importance" in CSS 2.1. If a rule has been given
'!important' then it wins over any non-important rule, period, end of
story. Two conflicting rules that have the same weight (or importance),
and thus have their conflict resolved through other means.
* Specificity -- how specific a selector is, which is figured out by
counting the pieces and coming up with a value. Higher specificity
trumps lower specificity, assuming the origin and weight are the same:
thus two normal-weight author rules that conflict are resolved using
selector specificity.
…and if, after all that, two rules are still in conflict, THEN the
order they're written in matters.
There's a little bit more to the story, once you take into account
inheritance and the lack of a notion of element proximity in the
document tree and so forth, but those are the core bits.
--
Eric A. Meyer - http://meyerweb.com/
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