Center standard WP gallery thumbnails

the standard gallery thumbnails in Wordpress are always aligned to the left side.
I would like modify CSS to align it to the center or right, but I don’t know how.
Can you help me?
Many thanks and compliments for your work,

P.S.: is it possible to give you a support via PayPal?

Add this code to Theme Options - Other - Custom CSS {
    float: none;
    text-align: center;

This will make images centered but there might be some problems with captions under some circumstances. If this is your case, then please let me know your website URL and I will try to help you from there.

Donations are highly appreciated and the best options is via PayPal where my ID is a.silkalns[at] (replace [at] with @ )

Thank you!

I’ve tried it, but it doesn’t work. I’ve sent you an e-mail with further informations…

Responded to your emails.

Let me know if there is anything else.