It sounds like the CSS stylesheets are taking a while to load (though it's unclear why it would be slower under FF than Chrome). Do you have any plugins installed that manipulate/alter page colors or layout (and might therefore slow down CSS)?
Just for laughs: In the old-style Firefox menus, select View -> Page Style -> No Style, and see if that bears a resemblance to what you're seeing (select -> Basic Page Style to restore normalcy).
I'm at a loss here. I used to be able to do a lot of this stuff but at 87 I seem to have forgotten way too much. Can't remember now where to find View, etc. Plus, I don't use Chrome browser much so still fumbling with that, AND haven't a clue how to navigate in this forum. Not sure how to upload a screenshot here but let me try doing it as an attachment...that is if I can find where the heck Windows 10 and Word stashed it..... Well that didn't go as planned. Having trouble saving the screenshot into a format acceptable here. Am going to go off and do something else for a while. this problem isn't going away so will take another stab at it tomorrow.
Thanks to all of you who have offered suggestions.