Version targeting was proposed by Microsoft for use in its Internet Explorer 8 product-in-development, but the idea was later discarded
The proposal came after the release of Internet Explorer 7 which improved its CSS 2.1 support at the cost of causing some websites that were developed for Internet Explorer 6 to be rendered incorrectly when viewed with the new browser version.
Microsoft contacted the Web Standards Project and experts on Web standards and asked for assistance in devising a new DOCTYPE-like technique that could work across browsers and let Web developers specify exact browser versions under which their Web sites are known to work correctly, and browsers implementing this form of version targeting would utilise the correct rendering engine versions to display the site correctly.
[...]
The concept of version targeting, especially as proposed by Microsoft, has been criticised for being a new form of browser sniffing and for violating the principle of forward-compatible development where progressive enhancement is preferred.

(Wikipedia)

The idea was dropped...
What is wrong with version targeting? Its great for developers, they have less checking to do as to if their old websites are still working in new browsers.
It shifts the work to the side of the browser developers, so frankly microsoft here is doing everyone a favor, taking work off web developers shoulders, so why do they receive criticism?

On the other hand I can understand the worries of open sources bodies, they are worrying about microsoft trying to slip control over web standards out of their hands.

more below...

http://en.wikipedia.org/wiki/Internet_Explorer_8#Version_targeting_and_backwards_compatibility