Looking at the page source (using a text-mode downloader), it seems it is mostly Javascript.
The best way to avoid these kinds of annoyances is to use NoScript.
It also seems to have a Flash object somewhere in the page. Flashblock can help with that.
There is also some code which moves windows all over the screen. Firefox has a preference which allows you to disable moving and resizing windows (dom.disable_window_move_resize); you should enable it (you do not need to use about:config for it, it is somewhere in the preferences dialog). While at that, also disable blocking the context menu (dom.event.contextmenu.enabled); it is in the same place in the preferences dialog.
Finally, the relevant bug report is Bug 61098 – Exit all currently active scripts (allow aborting modal window.alert() loops in javascript (js)) (warning: over 200 comments on that bug report). Finding a solution to bug 61098 (and coding it) will be a large step on avoiding this problem.
Edit: an even better bug report is bug 432687, which is the meta-bug tracking all bug reports relevant to this problem.