Hello,
I'll try to explain you how it works. Width of container for each thumbnail we calculate automatically with Javascript. Width of thumbnail container depends from parent container.
For example, you parent container has width 1000px, you have 4 columns, so thumbnail container is 250px - 4px space between thumbnails. and problem comes here. To hold thumbnails in a 1 line some, width can be changed, in another way, grid will be broken
So, the best to set 0px, 5px, 10px etc. between thumbnails
and also width of each browser little bit different, but we can't affect on it
Regards,