With the recent update of the post timeline page coming out today, I've noticed a bug in Firefox.
Steps to reproduce:
Go to a question's timeline page. For example: this one.
Click on the arrow near any "edited" lines to expand the edited preview of the post.
You'll notice that the timeline shifts to right-alignment when the post preview is displayed, instead of staying left-aligned. This is true for any type of edit (post, tags, etc.).
I'm assuming this is a bug and that the timeline should not be jumping around the page like this in Firefox, since it doesn't do this in Chrome. Visual examples: