My investigation of https://github.com/wild-flame/jekyll-simple/issues/13 leads me to suspect Skeleton CSS  You can see this on getskeleton.com itself:  Tested on Chromium 83 and Firefox 78
My investigation of wild-flame/jekyll-simple#13 leads me to suspect Skeleton CSS
You can see this on getskeleton.com itself:
Tested on Chromium 83 and Firefox 78