It's funny how many comments with the same opinion here get downvoted but no explanations why it's fine to add your own extensions to HTML/CSS (hello good old IE days). At least make your statements when downvoting so many people.
I think the problem is that your post doesn't read as if you're very well informed. You complain about apple-specific "tags" in a nebulous, hand-wavey manner, and all I can imagine is that you're actually talking about vendor-specific CSS properties.
And there's the problem: you're complaining about what you think is a violation of the CSS spec by making a reference to a mechanism and practice that was deliberately baked into it.
The authors of the CSS spec specifically accommodated vendor-specific extensions to give browser authors a place to work on supporting emerging abilities that are still in a state of flux. It's a special namespace where features are allowed to incubate. When these relevant standards leave draft status and become 'candidate recommendations', then a simple change will allow browser vendors to support whatever CSS property syntax is approved. When this happens, updating content on the web is an extremely easy change. This mechanism allows browser vendors and spec writers to work concurrently without creating a mess.
So, it's kind of funny that you're complaining about this when Apple is actually doing the right thing according to the letter and spirit of the spec:
Edit to head your next objection off at the pass: Yes, the spec also suggests that "authors should avoid vendor-specific extensions". This is a message to web developers, not browser developers. Apple does not want a web where every CSS file has "-webkit-" properties in it. They want these emerging standards to be ratified so that the vendor-specific properties can graduate to an official, approved syntax.
