These may be treated as safe.
try entering firefox safe mode and check disable addons
Mozilla Firefox have many addons, you can find alot of them on their site.
Hide Caption, exactly addons you need !
Go to Firefox.com, click Addons, and in the sidebar click Plugins.
The browser using the most memory is firefox. But it depends upon the number of addons and plugins used along with it. Chrome with 10 extension takes alot more ram than firefox running without addons.
open firefox, click on tools, click on addons, click on the addon you want to remove and click on Uninstall on the bottom right corner.
Getting Rid of toolbars can be a pain, but there is a simple addon for modzilla firefox, which will help to remove and prevent future addons,
on google chrome or firefox you can easily do it. get Ad Blocker plus from the chrome webstore(its free) and on firefox get Ad blocker plus from the addons( its also free)
I would try disabling some addons you may have installed. Gmail works perfectly fine with a clean Firefox install, so it's probably a third-party problem.
Compared to other web browsers Mozilla Firefox is fast loading, taking less CPU and processing load. Good compatibility of addons and less crashing or hanging problems.
If you mean Browsers FireFox is fast and stable, along with Opera and Chrome. IE8 is ok also, my reccomendation is firefox because of it's huge ammounts of plugins, addons, fast speed, security and stability.
Without any plugins or addons installed, you can expect to see 150-200 MB used.