This is in all browsers and in three different pc.
Without change settings you can see it again in my dev site, when you find some time free.
I had it with default color before
Thanks
EDIT:
After many test i addressed the issue. I have this mod
Chiplove.9xpro - Thread Thumbnails (not this in vborg)
It was made for me, with changes for my needs.
*When forums are active to show thumbnails i see that css line as i describe.
If i except them, css is ok.
* How come only if i change the default css color? Any way i must live with this if i not find it