Simply include the script in your pages and selectivizr will

CSS3 selectors for IE

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.

要するに、IEでCSSの属性セレクタを使えるようにするライブラリです。