uniring

__block NSView *bView = self;
[NSAnimationContext runAnimationGroup:^(NSAnimationContext *context) {
    context.duration = 0.3;
    context.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
    [[bView animator] setAlphaValue:0];
} completionHandler:^{
    [bView removeFromSuperview];
}];

uniring

-webkit-background-clip: padding-box;
-webkit-border-radius: 5px;
-moz-border-radius: 5px;
border-radius: 5px;