The forum has recently been under attack by injection of malicious Javascript as described by the forum administrator here.
The symptoms of the injection are that you are randomly redirected to some porn/advertising site when clicking on links or answering posts.
The problem has apparently been fixed, however you are strongly recommended to clear your browser cache to remove the Javascript from the cache.
For instructions on doing that Google for:
how to clear browser cache
The first hit, which seems reasonably reliable, is How do I clear my web browser's cache, cookies, and history?
In most computer-based web browsers, to open menus used to clear your cache, cookies, and history, press Ctrl-Shift-Delete (Windows) or Command-Shift-Delete (Mac). If this doesn't work, follow the appropriate instructions (on the linked page).