This is my jsFiddle, which I have taken from my previous question here.
The CSS is:
#logo {
position: absolute;
left: 2%;
}
@media (max-width: 500px) {
.ui-block-solo { flex-direction: column; }
#logo { position: static; }
}
Now see how it looks in Chrome:
Now see how it looks in Mozilla:

See how the logo falls goes out of the header? How to fix this?
Mozilla version: 40.0.3. However, one of my users spotted the issue, but I do not know the version of his Mozilla.