I have noticed this issue over the last month or so & figured it would be fixed in new versions, but it's still there. And hard to describe!

I follow numerous sites via RSS & load a couple of sites at a time using "Load this feed in tabs". I have noticed that on some sites (makeuseof.com is one of them), when I go to the first tab, Firefox briefly displays the contents of the next tab before switching to the one it should be displaying. It happens mostly when there are lots of tabs present.

Curious as to whether anyone else has seen this behaviour.