I have a margin problem on some of my pages, those where I have integrated an HTML part.
At the very top, my first Layout Grid is slightly off. Here's a photo:

I found a solution by modifying the .css file
I need to remove a margin located in a body tag (margin: 20px).

I'm currently deleting this by hand, but I'd like to know if it's possible to modify this data directly from the software so that I don't have to deal with it again.
Thanks a lot