changing javascript settings

Hi,

We have a client who keeps running into problems trying to access
number of javascript applications through out their website. We've
narrowed it down to their Javascript settings. It only happens when
'Disable or replace context menus' is checked (Firefox). They claim
they do not change this, but it seems to happen a few times a week.
Does anyone know if these settings can be changed externalyl? Via a
website for example?

Thanks
SWS
.