The “all” property looks interesting as I know this question has been asked numerous times over the years.
e.g.“How can I drop an element/widget into my page and not have it inherit any styles that might break it”.
It would seem that you could then use pre-made modular structures and just drop them into pages as required. Of course it seems that if you built the whole page like that then you couldn’t make any global changes easily.
Hm, Interesting, although I wonder if it’s just another one of those innovations to account for bad web design practices.
I think its there to address the problem of inserting pre-made widgets into existing pages rather than something the author of the page itself would need to worry about but of course it would be open to abuse like many other properties.
(I actually needed the opposite of this the other day as a client had a CMS that allowed users to enter html but didn’t want them adding their own styles which the editor allowed (and which were applied inline). I had to set a load of !important rules up to try and catch anything the user may have entered (assuming they didn’t know about !important of course). It was easier than the client changing the CMS which would have been the correct solution.)
Similalry, I have added a load of extra styling to my Twitter feed where it is embedded on my website to improve the look of it and integrate it better into the overall design – I don’t want the peeps at Twitter to then be able to override thsoe styles!