Hey I'm a moderator of a xenforo forum (this one) though not the licence-holder or anything. I was having problems with lag when typing, and myself and the owner discussed whether the amount of posts per thread page affected it (he had it on 50, then we changed it down to 20 and it felt to me that the lag [page loading; time for what I type in the text box to appear] was reduced). What I want to know is, firstly, does the amount of pages visible per thread affect the lag to anything close to a significant degree, and does anyone have any tips for reducing the lag other than I've discussed in this paragraph?
Client lag like this can of course be the result of an extremely slow computer. But if your computer is not to blame then perhaps something on the web page is consuming resources. It could be runaway js or some type of media on the page that is eating render time.