I noticed something strange. I finished this website a few weeks a go and everything looked normal. Today i noticed there are some white lines/spaces between the images in the grid.
The "cross" doesn't show on my browser. The problem with white lines is due to a problem with browser counting mathematically width of elements, and where width of containing element is odd, there is a glitch. I'll ask our dev team about is, as I'm pretty sure it was fixed already.
The problem is mainly on chrome and sadly - it is browser calculating wrong sizes issue. The only "part solution" is to change background under the tiles for dark one so it blends better with the tiles.