The DOCTYPE switch is broken

1998
Todd Fahrner
a toggle that
allow a browser
two rendering modes
a well-formed DOCTYPE
made the DOCTYPE unsustainable
developers of authoring tools began inserting valid, complete DOCTYPEs into the markup their tools generated
IE6’s rendering behavior was not updated for five years
When IE 7 hit the streets, sites broke.
Chris Wilson
has often said that one of the core tenets of development on IE is that any choices the IE team makes must not
“break the web”
IE7 did just that for quite a number of people
Unwilling to make the same mistake twice
Microsoft
asked for our help in coming up with a better method
Microsoft Office 2007
cannot reliably render a Word 1.0 document

Targeting a browser version

<meta http-equiv="X-UA-Compatible" content="IE=8;FF=3;OtherUA=4" />
does version targeting spell the end of progressive enhancement?
no.
living on the “edge”
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
strongly discouraged