My first inclination would be that you may have drove through something, such as melting snow/salt, that stained the tire temporarily. I'd suggest letting your tire dealer have a look.
My new Continentals have marking like that as well. They come like that, don't know why. It will come off after a few rains.
Seen it on Michelins and Generals, as well.
Now go have a beer.
I'm not seeing the photos. Just two small "image" squares. Also, it appears they are hosted on a Google user site.
I suspect this has more to do with the permissions set for viewing the photos at the hosting site than with the browsers being used for this (SubaruOutback.org) website. @eagleeye: If you can see the photos in the posts, perhaps if you copy them, and then post them as attachments, they will be readily seen by all, at least until the OP sees the problem and checks the settings.