Hi!
I'm using child theme with overriding parrent theme styles.
The promblem is in duplicating style classes. After activating option "Optimize CSS Code" there is some bug on page reload (CTRL+F5). For some reason it apply some strange styles for half a second, that are not visible when option is disabled. So website design just for a moment on load looks strange. Optimized css file stores both style classes - original and overring.
Maybe such scenario would fix it.
1. get parent theme css first.
2. get child theme css.
3. remove styles from parent theme that are in the child (parent theme styles minus child theme styles (styles in classes, but now whole classes complitely)).
4. split styles (parent theme style plus child theme style).
Enabling "Inline all CSS" option fix the problem, but it is not what I need.
Screenshots (after activating option "Optimize CSS Code").
1. blue text instead of white with little move-in effect (it is really set to white in both parent and child theme, but for some reason shows blue): http://oi59.tinypic.com/vq6v41.jpg
2. sliding forms from right screen side (problem doesn't appers when option is disable) and blue text again: http://oi60.tinypic.com/33p7szs.jpg
3. and so on ..
P.s. I was able to reproduce the issue only with non-admin login.
Thank you!