I've been experiencing an issue with the tabs and lag as well. The lag only onset like a day or two ago, but I've been really noticing it tonight. That's just across the whole forum. "Lag" in this case refers to slow loading times in general, both when logged in and logged out.

As for the tabs on profiles, all of them except Visitor Messages and Friends don't open when clicked on when I'm using my phone, and take a really long time to load on my laptop. I've been experiencing that since I signed up. Again, this happens both when logged in and logged out. It also happens regardless of what skin I'm using (ie happens in both desktop and mobile mode)

I use an iPhone 4 running iOS7 using Safari, and a laptop running Windows 8 using Google Chrome, both on home wi-fi.

(On a somewhat unrelated note, I can't open spoilers when using mobile mode on my phone, but can when using desktop mode on it. Just thought I'd throw that in there!)