I wondered the same thing so let me save you the search:

> http://help.dottoro.com/ljlumkqh.php

The page implies that there is limitations to the IE8 implementation, and that it's only available in relatively recent browsers. In addition, I believe that sizzle implements a set of selectors larger than most or all browsers support natively, although this I am less sure of; the Sizzle documentation certainly implies it strongly:

> https://github.com/jeresig/sizzle/wiki