Websites may change their layout depending on screen resolution (responsive design) or may redirect to a mobile site.

With responsive design, there's not a universal agreement on when the layout should change (for example, it might be close to 1000 pixels horizontally, or under 800 pixels). Usually you need to experiment by zooming out one or two steps (hold down Ctrl and tap the - key once or twice) to find the point at which the layout changes.

If you are getting redirected to a mobile site, that could be a decision the site is making in real time, or it might be a choice that has been stored in a cookie for the site. If you see this happen, can you find a way to view the desktop version of the site?

For more context: in your other thread, you mentioned:

It only happens on LinkedIn and Facebook?

You may have accidentally zoomed webpage(s). Reset the page zoom on pages that cause problems.

• View -> Zoom -> Reset (Ctrl+0/Command+0 (zero))

• https://support.mozilla.org/en-US/kb/font-size-and-zoom-increase-size-of-web-pages