Not sure if I’m misunderstanding your issue, but this is default behavior of a web browser and has nothing to do with Webflow or your website at all. As far as turning them off goes, Chrome removed the ability to do this at least a year ago.
Thanks for clarifying, I didn’t even notice in your example at first. I do see this problem on the live site, as well as in the designer, but only on the home page. I don’t see anything changing when inspecting the source code as the boxes appear, and I can’t even inspect whatever the specific element might be causing this. I can also see that the boxes don’t even align with the positioning of the containers on the page.
This is really strange, and I’m going to recommend you open a support ticket with Webflow directly in this case. Would be really curious to know the cause though.