I think it's not working, I've try it for ie 8, use image do not use css radius, it's not working for ie
What the devil is a "radius curve"?!? -- do you mean border-radius? If so, then yes, it works in IE9, no there is no such thing in IE8/lower since that's a CSS3 property. ... and I would NOT worry about IE8/lower *oh noes* not getting rounded corners or any other CSS3 properties... and do NOT waste time adding any javascript shiv/polyfill asshattery for it. So long as the page is still functional for those legacy browsers (which lacking CSS3 they should still be) don't waste time bending over backwards to support people who refuse to join us in THIS decade.
Why you should use image just to get quirky corners, you can achieve border radius in modern browsers and IE9+, you can avoid extra HTTP request by eliminating curve image sprite.