Hi, there is small bug with Lightbox - if opened on second+ image on page - page can be horisontally scrolled.
Demo here: https://xenforo.com/community/threads/testing-lightbox-hs.115533/
Reproduce tip: click on images in second post.
Used browsers: Firefox 48, Chromium 50 on Linux with 1366x768 screen
Phone browsers looks like not affected.
On Linux - system "Ubuntu Regular 10pt" font, also applied to browsers. Windows host - vanilla configs. Any zoom disabled both on Chromium and Firefox.
Update for way to reproduse: open lightbox for first image on page (in 1st post), all looks like normal. Close lightbox, open first image from second box - horisontal scroll appears.
I can confirm this on MS Windows 7 / IE 11. The scrollbar appears on the second or third opened image, but never on the first. The opening order doesn't matter after page refresh. Only the 2nd or 3rd opended pic, never the first is affected.