Need help - github pages renders things weird, why?

full res image

https://github.com/JuggernOtt81/Bootstrap-Grid-Templates
https://juggernott81.github.io/Bootstrap-Grid-Templates/index.html

when i publish my code on github pages, it partly breaks.
makes pages 2 and 5 look completely empty.
not sure why.
seems to make no sense.

just noticed i had forget the links.
but now i’ve edited to add them.

while I sincerely remember changing to this:

<link href="https://juggernott81.github.io/Bootstrap-Grid-Templates/css/site.css" rel="stylesheet">

from this:

<link href="/css/site.css" rel="stylesheet">

somehow, the change was only committed on the index.html page and none of the others.

but I’ve fixed this and committed on all pages.