X-UA-Compatible: Sensible Defaults

I’ll keep this short((well, short-ish)), because last time I rambled, and basically failed to make clear what I thought the problem was. In the end, my problem with the whole X-UA-Compatible concept was really in what IE8 planned to do when it was absent, which was to pretend it was IE7.

Yesterday the IE team posted an update announcing that IE8 will default to behaving as IE8 in standards mode, with IE6 or IE7 standards mode optionally available via X-UA-Compatible. This was my “wouldn’t it be nice if… too bad it’ll never happen” outcome1. I’m happy to have been wrong about the latter((By extension, I’m happy Rob was wrong.)).

Eric Meyer, who wrote one of the two articles on A List Apart that started off this whole discussion, posted his reaction to the change yesterday. While generally very positive, he makes an important observation:

I think what worries me most is the possibility that when the public beta hits, there will be enough incompatibility problems that pushback from other constiuencies forces a change back to the original behavior. I hope not. I hope that what will happen is that any problems that come up will be addressed by spreading the news far and wide that there’s a simple one-line fix for those sites.

I’m sure there will be more information forthcoming as IE8 betas are relased, but here’s what I’m taking away from this. If you develop/maintain a web site/application/etc. you need to be aware of these upcoming changes. If your site/application/etc. only works/looks right in IE7 and don’t intend to change that, you should probably add <meta http-equiv="X-UA-Compatible" content="IE=7" /> to your page headers now, to ensure that IE8 continues to behave as IE72. If you’re site/application/etc. works cross browser3 you’re probably in pretty good shape, but time will tell.

  1. Being somewhat optimistic, Rob had to convince me it would never happen []
  2. I’m assuming if you still develop primarily for IE6 you either have no other choice, or you’re insane. []
  3. I’m a strong proponent of this. Mostly because I find developing to the most standards compliant browser and then fixing browser specific quirks much less maddening than the reverse. []

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