or do these just popup before any browser is even opened?

eg. where I am located, when you go to certain fast food joints that offer free wifi
you have to open your browser first
then attempt to make the connection
which then opens a new tab in the browser window to the "Terms of Service" page
where you click OK you agree to the ToS, before you can get on the network to access the web
_ _

if these popups do come through the browser, would;
A> disabling the the browsers plug ins help in lower the chance of seeing one of these popups
eg. disabling, the Reader, QuickTime, etc. plug ins

and
B> would using Firefox with NoScript help as well?