The WP start screen (live tiles) contains an unintented optical illusion

[Josip Zeljko]

I don't know if you guys have noticed, but if you look slightly away from the tiles you will see small grey circles appear in the blank space between the edges of the tiles. The effect is even stronger when using the white theme and brighter color theme.

 

[BataBole]

Mo?e biti da ti je ispao telefon i prilikom udarca se displej o?tetio pa su ostale te pjege na ekranu. Nije softverski problem.

 

[steve_w_7]

This is called the Hermann Grid Illusion. Look it up on Wikipedia. Trippy!

 

[Josip Zeljko]

This is called the Hermann Grid Illusion. Look it up on Wikipedia. Trippy!

Yep that's it.
From wikipedia: " The Hermann grid illusion is an optical illusion reported by Ludimar Hermann in 1870.[1] The illusion is characterized by "ghostlike" grey blobs perceived at the intersections of a white (or light-colored) grid on a black background. The grey blobs disappear when looking directly at an intersection. This illusion can be observed in the Flag of Cornwall."