Photospace plug in has extra small square

I have funny little black squares showing up on my screen. I am on a mac, but my friend on a pc don’t see them. I would like to remove them so they don’t show up on a mac.

Also, is there a tutorial on how to adjust the style sheet? I want to decrease the gray behind the thumbnails and bring the padding up on the top between images and text. It’s a little different than what I’m used to working with on the WP css sheet.

here is the link
https://creative-matter.com/blancafloral/?page_id=65