My front/home page when logged out used to look very different than now, using Grey Amber theme. The text overshoots past the gray background (see below). I haven’t changed anything in my HTML/CSS edits within a year so there must have been an update that changed the page layout. I also used to have the login button on the top right. It got moved to the bottom of the page. Instead, at the top, I have my mini logo image, which should not be there. I only used to see the big image.
Yes, we’ve changed the default to be more stylized, which unfortunately has the effect of clashing with sites that added their own styles. Taking a look at your site… I think adding this CSS would get you closer back to where you were: