The Google Chrome Frame <meta> tag throws an error to the W3C validator because the http-equiv value of "X-UA-Compatible" is not recognized by the W3C/WHATWG as a valid value. As Chrome Frame is a powerful and exciting web service, I am anticipating this will be recognized as valid in the future, and have thus chosen to keep the Chrome Frame service as a part of my web pages.
Further, it is my understanding that http-equiv values begin with "X-" under XHTML1 to signify they did not need to be validated. I also assume this, or something similar, will become the HTML5 standard soon.
Finally, I don't believe generally that values should be presubmitted to be valid, unless this is absolutely required for technical reasons. I don't claim to be an expert in this matter, so I fully admit that may be the case.
