This looks like its the result of using something like bootstrap (which I see in the source, is in fact used here).

Basically you have CSS designed to detect a mobile device and adjust everything when found. It does so using the window size. So adjusting your window can cause the screen to go into mobile mode - where buttons get moved and things go single column, etc...

But if mixed with other plugins that use different methods for mobile detection, it can get really weird when not actually on a mobile device - and you get things like ads displaying over places that have moved because they think they're mobile.

Bootstrap is great - I love that plugin and use it myself at my work. It really smoothes out a lot of CSS issues. But it also assumes people are on more modern displays and that the chances of them zooming the display, using a small resolution, or even using a window that is much smaller than the rest of the screen... are small.

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