Have had a couple of reports of the site intermittently shifting / scrolling / or sliding when pages load, but have never experienced this myself.
If anyone else is seeing this and you can provide some or all of the following information, I'd appreciate it:
Which browser you are using
Does the thread contain unread posts when it happens
How are you clicking to get into the thread (ie. clicking on the title or the 'dot' to indicate unread posts
Do the new posts sp