YUI3 selector problem in ie8

Y.one('form fieldset:nth-child(2)').toggleClass('hide');

in chrome, FF, opera this line works but in ie6-8 it throws an er开发者_开发百科ror 'Y.one(...)' is null or not an object.

where is the problem?

Have to add the "selector-css3" module to your .use() statement if you want to use CSS3 selectors in browsers that don't support them natively.