Which browser versions do YouTube and Google Apps support?

We're building a site and wish to build开发者_开发问答 for the same set of browsers Google Apps/Docs and YouTube support. Though not recommended, they seem to be detecting specific browsers/versions vs. features/functionality. What's the best way to support a minimum set of browsers while displaying a message to the users of older browsers to upgrade? What's the minimum set of browsers that the major sites are supporting? Thanks.

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You can take a look at browsers usage statistics here:

http://en.wikipedia.org/wiki/Usage_share_of_web_browsers

IE6 is becoming less used than it's newer versions and, because of it's obsolescence, lack of proper CSS support, and Javascript engine performance, it's difficult to fully-support it (see http://www.google.com/support/youtube/bin/answer.py?hl=en&answer=157259).

You can choose then to support all the four major browsers: IE7 and above, FF 3 and above, Chrome 3, Safari 3 and above, which cover >87% of the users.

Anyway, if it's important to you, you can choose to offer a feature-limited version for older browsers (but most of the times that would imply building another web-app: more work, more time to spend on it) .

It basically depends on how much your web app uses certain 'advanced' features, and the importance to target older browser's users.