Layout alignment gone wrong! looks ok on windows but terrible on mac?

Hey guys,
I’m relatively new to webflow, still learning and implementing as I go and I was wondering why everytime I’m in design mode, everything starts centered and by the end of creation, it’s as though I’ve been working left of centre the whole time.

Is this a browser problem or a containment problem? I am using Windows and I always work full screen to ensure everything is being laid out properly, and it does actually look correct for me on Windows but when I asked a friend to view it from her mac; nothing is centred and some elements show up askew.

Here is my site Read-Only: