[MerLock]

It wasn't the border that I initially noticed. I was reading an ebook where there was minimal margins on the top and bottom of the screen. When the first line of the text lined up with the top edge of the screen, I noticed that it was a bit skewed and it started to annoy me. I was surprised at how easy it was for my eyes to detect the crooked text even though the screen appeared to be off by just a millimeter or less.

I then put the screen further away and looked at the page numbers on the bottom border since that's pretty close to the bottom edge and could tell it was crooked.

By the way, I could only really notice the border in strong light. It was the first line of text on the top that was noticeably crooked.

I'm not sure if that's how lev first noticed it.