Not sure if this is something that y'all can help with since it's not a theme or plug in directly from you?
I'm rebuilding my blog (heck, my entire site) because some might recall the WP installation was hopelessly done for, and then unrelated, the server itself crashed. In trying to restore everything, somehow my ex turned my site into Joe's Apartment. To get rid of all the bugs, we had to nuke the entire site from orbit. Only way to be sure. Since I wanted to do a total overhaul anyway, it wasn't a big deal.
I'm working on a new design layout for my blog, using the theme "Jolene". On my Firefox browser, (47.0.1, with the following plugins: Adblock Plus (Last Updated Thurs April 28, 2016), Add Bookmark Here, Copy as Plain Text, Copy Link Text, Easy Copy, FireFTP, Flash Video Downloader, Gmail Notifier, Lazarus, LJ Account Juggler, Personas Plus, RightToClick, Status-4-Evar, TabMixPlus, TabGroupsManager, Web Of Trust) It renders properly.
It renders properly on Chrome, Version 53.0.2785.116 m (64-bit), as well as Edge (which is letting me no longer recoil and hiss and look for holy water whenever a Windows browser pops up now.)
BUT. (you knew that was coming or I wouldn't be here.) My wife, who also has Firefox, and up to date, has only these ad-ons: adblock plus, copy as plain text, copy link text, gmail notifier, LJ account juggler, Right to click, tabmixplus, web of trust. Less than I do.
And I checked the rendering of the site for mobile/tablets, and it should display correctly. But on my Google Nexus tablet using a Dolphin browser, I wound up with the same problem she did.
The problem she had, and the Dolphin had was the left sidebars stretched over the full extent of the page, and the center actual blog entry area was pushed way to the bottom and had no lighter background color and the text was all smushed up together. (She's downstairs on the laptop Skyping with her father. I'm going to have her check the blog on the laptop; either way, I'll get a screencap of how badly borked it renders on her desktop soon.)
I overall like the looks of this, but I still want to tweak it more, which would mean doing some custom CSS, and I don't want to bother with that much if the whole theme needs to just be scrapped because it's not going to work for most people.
EDIT: Okay, it renders correctly on wife's Firefox on the laptop, and NOW the desktop is behaving for her. Still arguing with my Google Nexus on Dophin, though.