I have a new-ish (five months old) Dell laptop with Windows 7 and am using Firefox 344.0.1 or whatever version they're up to these days.
I often have multiple tabs open to different pages, as I prefer that over separate windows.
There are only a couple of ways I know of to switch tabs. One is through keyboard shortcuts (either Ctrl + PageUp/PageDn, or Ctrl+Tab/Ctrl+Shift+Tab), and the other is by pointing my mouse at the other tab I want, and clicking on it.
Occasionally, when I'm scrolling or moving my mouse pointer around with the touchpad, Firefox will move over to the next tab for no apparent reason (that I'm aware of). I haven't yet figured out what I might be doing to cause this to occur, and a google search didn't reveal anything that suggests a default setting for a specific touchpad gesture that causes the tabs to change.
I've already ruled out something as simple as me having the pointer over another tab and accidentally tapping (clicking) when I'm trying to scroll, because the mouse pointer isn't anywhere near the tab bar when it happens.
It doesn't happen when I use a regular mouse, only when I use the touchpad, so I figure there must be some shortcut in place that's causing it, I just haven't found it yet.
Any ideas out there?