Imagine for a moment what would happen if Adidas or Reebok began giving away free shoe liners for the ostensible purpose of making Nike shoes comfortable enough to wear. It would be something of a slap in the face to Nike.That's not far from what happened on Tuesday when Google released Google Chrome Frame, an open source plug-in that turns Microsoft Internet Explorer into "a modern Web browser," to use the term favored by Google and Mozilla for recent browsers that are not Internet Explorer.

Google Chrome Frame literally creates a version of the Google Chrome browser inside Internet Explorer. It turns Internet Explorer into window dressing. Its purpose is to allow Web developers "to take advantage of the latest open Web technologies, even in Internet Explorer."

Such technologies include faster Javascript and HTML 5 features like offline storage, the canvas, video, and audio tags, and improved CSS.

Adding insult to injury, Google has enabled Chrome Frame using the X-UA-Compatible header that Microsoft extended to make Internet Explorer 8 able to emulate Internet Explorer 7. The technology that Microsoft used to ease compatibility problems has been conscripted by Google to shine a spotlight on Internet Explorer's compatibility problems.

Google Chrome Frame is available as a download for Internet Explorer 6, 7, and 8 on Windows Vista / XP SP2. But it's not as subversive as it could be because Web pages must contain a meta tag using the X-UA-Compatible header to enable the Chrome Frame. It's easy enough to add, but most Web pages won't use it. If Chrome Frame could be invoked without any Web page changes, that would really be dangerous for Microsoft.

Even so, the mere existence of Chrome Frame has to be galling for Microsoft, which has actually been making noises recently about being more involved in the development of Web standards.

Framing Web pages that belong to someone else remains a practice that publishers hate and many see as copyright infringement.

Google, meanwhile, characterizes the act of turning a browser into nothing but a frame for the competition as an effort to make "life easier for Web developers as well as users."

It's also an effort to prepare the world for the coming of Google Wave, which doesn't work so well with Internet Explorer.

"In the past, the Google Wave team has spent countless hours solely on improving the experience of running Google Wave in Internet Explorer," explain Google Wave team manager Lars Rasmussen and Google Wave client tech lead Adam Schuck in a blog post. "We could continue in this fashion, but using Google Chrome Frame instead lets us invest all that engineering time in more features for all our users, without leaving Internet Explorer users behind."

Elsewhere on the Web, the popularity of sentiment like "IE6 Must Die for the Web to Move On," suggests that Google Chrome Frame has some ready-made fans.