Better Javascript Control
Firefox without add-ons allows to enable or disable Javascript. If you uninstall the popular Noscript you can enable Javascript on trusted websites and disable it on all other websites. If you want a better Javascript control in Firefox you could take a look at the Firefox add-on Controle de Scripts which gives you a much deeper control of what Javascript may do and may not do.
The Firefox add-on has basically two tabs that control certain Javascript functions. The main tab is called Permissions and you can allow or disallow functions like resizing windows, changing images, hiding scrollbars or the bookmarks toolbar here. The second tab is Popups which defines which Javascript events are allowed to open popups.
Knowledge of Javascript events is needed to configure this properly, you could use Google to search for the Javascript events as well . You might be saying that you don’t want any popups but you might consider that some websites open new pages in a popup after submitting a form or clicking on a link.
Control Javascript Events in Firefox said...
[...] Firefox Mastery published a nice article about the Firefox add-on Controle de Scripts which lets the user control Javascript events in Firefox. Instead of just disabling Javascript (default Firefox without add-ons), or enabling it on a per-site basis (NoScript) you can configure and control specific Javascripts events. [...]