[whatwg] <meta http-equiv="X-UA-Compatible" content="IE=edge" />

[Brenton Strine]

By now, everyone has heard that IE8 'passes' the Acid2
test, but (To paraphrase Jeremy Keith:
http://adactio.com/journal/1402/) won't render pages with
the new standards-compatibility unless you explicitly
tell it to with this meta tag:

<meta http-equiv="X-UA-Compatible" content="IE=edge" />

--i.e. it actually won't pass Acid2 because the test
doesn't have that meta tag in it. I agree with Jeremy
that this is a mistake. One of the reasons I write
standards-compatible code is so that my websites will
work in future browsers when they support new/better
features. All such webpages are effectively locked into
IE7 now, and won't get any benefits of the newer browsers
unless I add this new meta tag. 

The example from the article is generated content. Since
IE8 isn't out the door yet, I wonder if we can't do
anything about this to prevent a bad situation for years
to come. 

My thought is this (and I'm hoping other people will come
up with better ideas). Give HTML the ability to declare
specific technologies that it uses, such that if a
browser supports that technology, it makes use of it.
Sort of like using object detection in javascript instead
of messing with the user agent string. For example,
assume an amazing new image format comes out called
AwesomeImg--Opera 11 supports it, but you're not sure
when IE will. Maybe IE10. But you don't want to lock your
site into IE10 mode because it might break in IE10, or
IE10 might still not support all your features but IE11
would have.

There should be a way to tell the browser it can
implement your technology without locking your website
into a specific version. A website can then avoid the use
of the "edge" attribute, which might cause future
breakage, but also would avoid being locked eternally in
the limitations of a specific browser version, be it IE7,
IE8, IE9, etc.

If we get this into the spec soon enough, Microsoft might
incorporate it in IE8 before it releases. What do you
think? Whether it's a good idea or a bad idea, I feel
that the whatwg needs to address this issue somehow.

Brenton Strine
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