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Note On CSS Inheritance

If, in your theme, you have the function wp_head() in the header.php file before your other style sheets it could conflict in your CSS inheritance, because they will be at a higher priority then the style sheets after the function call.

I suggest having the wp_head() function place right before the end of the section to remove any possible CSS conflicts. You can add the !important attribute into your peristent style sheet that you want to have priority.