Hi. I'm trying to switch from chrome to firefox, and I see this strange, thick gray border/padding around the content of every page I view in the browser. It's perfectly consistent between tabs and not part of the actual web pages. It grows and shrinks as I resize the window. It makes everything a bit smaller than it is in chrome. I haven't been able to search and discover what it is/a solution, because the terms I try to search for produce different topics. What is this? Is there a setting I can change to turn it off?