Center thumbnails. Read pls i've look for other solutions

I know that this problem has beed treated lot of times, but the problem is that all the solution regarding code to add or change in nggallery.css.

Now with the last update i have a nggallery.css empty that sad:
“This stylesheet is provided to allow users the ability of overriding the default styles for all display types”

Anyone has fixed the problem editing this file or not?
I see that all the solution works for some people but not for all, now could please the author say us where we can change code to put the thumbnails at the middle of the page.

I can change style from option but nothing reguarding the alignement????

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