This property takes an Internet Explorer Conditional Comment. For example, if we wanted to link to a style sheet specific to IE 7 or greater, we can do this:

<SharePoint:CSSRegistration Name="foo.css" ConditionalExpression="gte IE 7" runat="server" />

The following markup would be emitted:

<!--[if gte IE 7]>
<link rel="stylesheet" type="text/css" href="foo.css"/>
<![endif]-->

• Much better JavaScript performance! IE8 was a nice first step at improving JS performance on IE but still woefully behind the JS profilers and JIT compilers of Firefox, Safari, et al. Early builds of IE9 are already 4 times faster in the SunSpider benchmark than that of IE8 and putting it about par with Firefox 3.5.
• CSS Level 3! Again early builds apparently are able to pass the majority of the CSS3 Selectors Testsuite, 41 out of 43. Of course, Firefox 3.5 and Safari 4 already completely pass this test. IE8 only passed 22 of these tests by the way.

Where’s more HTML5?

Microsoft was very non-committal about this. They made a good start in IE8 with things like DOM storage, cross document messaging (XDM) and have a built in JSON API, but where’s <video> or more importantly <canvas>?

It’s a promising start for Microsoft with news about IE9′s JS performance and CSS3 compliance. Here’s hoping to Microsoft finding time to implement some of the HTML elements that competitors have already integrated into their browsers. Don’t need IE10 to STILL be playing catch-up.