Just on this site and it just started since this new back ground has been added. Don't know if that has anything to do with it or not.,
Hmm, unsure how it would affect scrolling.
I added a shadow to the forum wrapper. The "wrapper" has always been here but just last night I added the rounded corners and shadow.
The background has also always been here, of course, but last night a simply added the image over the background then set the background image as fixed so the forum appears to float over the background.
Im using IE11 and with the simple VTT it scrolls nicely again now. Your background is fixed and that could be it. If the background scrolled with the content perhaps it wouldn't do that. I don't know. My backgrounds on my websites are fixed also and it doesn't affect them.
God grant me the strength to restore the trailers I can, The courage to strip the parts off the ones I can't, And the wisdom to know the difference...
I went in my profile and switched back to the simple and it seemed to make a huge difference when I got rid of the pretty trim. Don't know if it solved all the problems but it helped.
I had been looking into why my Firefox takes awhile to completely close (monitored via my Process list), so checked my FF and plugins for updates and after updating it's still slow on completely closing. I then set all my plugins to "Ask to Activate" except for one, Flash (which I set to "Always"), this basically disables the plugins from running; still the same issue.
While my plugins were disabled (aside from Flash) I popped in over here and was getting serious lag when scrolling.
I switched themes to see if there was any change and got the same sub-par performance.
Checked several other Proboard sites; same issue. So I went and set all my plugins back to always and now sites are scrolling fine as they should be.
So, FF still slow to close completely (6 to 12 sec.) but I did find that my plugins could affect scrolling. At least in my scenario.
YMMV, being that you got some improvement just by changing themes.