I don’t know why this is happening.
I have this code here.
It works fine but “sometimes” (and many times in a row) for no apparent reason, this happens:

To all the .box class.
Sorry I have to share “all” my code but I have no idea why this is.
This is what it should look like:

I don’t know if this is usual but id you want, you can download the two files from here (HTML and CSS + Images) because in jsfiddle seems to work all of the times,
I don’t know whether it matters or not but I’m using chrome (latest) on a mac.
EDIT: I seems to work fine in safari every time.
Thanks in advance!! Please ask for any clarification needed!
By the way my title is absolutely horrible, sorry! but I have no idea what the problem is so I can’t really describe it, feel free to edit or comment any suggestion.
On your
style.cssoverflow:hiddenon#containeroverflow:hiddento the.boxfloat:leftto the.box imgfloat:rightto the.follownew