Do you need to emulate CSS3 selectors in Internet Explorer 6, 7 or 8? This is exactly what SelectVizr JavaScript utility will do for you!
"Selectivizr is a JavaScript utility that emulates CSS3 pseudo-classes and attribute selectors in Internet Explorer 6-8. Simply include the script in your pages and selectivizr will do the rest." From: http://selectivizr.com/

In case you want to know more about how IE8 is supporting CSS3 then you take a look at an in-depth article on James' Blog about Internet Explorer 8 and CSS3.
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