Microsoft has recently announced that Internet Explorer 8 will contain not one, not two, but three different rendering modes: Quirks mode (IE6), Standards mode (IE7), and We'll-Try-HarderTM mode (IE8), from here on referred to as WTH.
IE8's WTH mode is basically what other standards-compliant web browsers, like Opera, Safari, Firefox, and pretty much any other browser that's Not-IETM, do already, namely render the pages to the best of their ability and stick to the standards as closely as possible.
Rather than follow suit and make IE8 render things like everyone else does, Microsoft has decided to bring us back to the bad old days of browser sniffing, content negotiation, and general suckiness that was the web before browser makers got serious about supporting real standards. To get IE8 to render in WTF mode, you need to include a Microsoft-specific META tag (or equivalent HTTP header) on every page. To make matters worse, we must be living in some sort of twilight-zone inspired alternate reality, because long-time standards advocate site A List Apart has gone over to the darkside and is actively shilling for Microsoft's asinine stance on this.
Instead of adding my two cents about why this is bad, I'm going to take another approach, and suggest a solution: Don't drink the Kool-Aid. Boycott the X-UA-Compatible header Microsoft is pushing, especially if you are concerned about coding to standards. Why? To force Microsoft to abandon WTH mode, make IE8 standards-compliant by default, and stop this ridiculous cause once and for all.
We can do this. By Microsoft's own admission, they are relying on those of us who care about standards compliance to add this tag to our pages; they don't expect older sites to do anything at all. Instead, just keep doing what you're doing -- writing standards-compliant sites. IE's market share is declining, and by the time IE8 ships and is widely deployed, it will likely be even less. Now is the time for standards to reign, not vendor lock-in. Make your voice heard!