I know that I have read it some place before, but I can't seem to find it, and I can't remember exactley how it goes...
When being a fighter, and leveling up on a specific lvl, you will gain +1 str, and if you have 18 str, and then uses a +1 str tattoo, so that you have 19 str when leveling and gaining the +1 str, you will then have 20 str with the tattoo.... if you then remove the tattoo, you will have 19 str base, and will have skipped all the 18/xx str's....
But at what lvl where you going to get the + str??

You don't need any tattoos for this. Just be at 18th strength when you hit level 7 as a fighter, and it will jump to 19.

And at what lvl does the fighter get + str again?

12th.

If you reach that level first in fighter class.

And 7th, as I said in my above post.

Of course Platter, but he asked what level again he'll get the specialization bonus. ;)

Thank you both

Oh, thought he meant like he was asking again.