How do I change the scrollbar in Firefox?
Nevertheless, you can still change that browser's scrollbar style to different alternatives within the browser's about:config (Advanced Preferences) menu. This is how you can customize Firefox's scrollbar style by changing a hidden flag on Firefox's Advanced Preferences tab.
How do I stop multiple tabs from opening in Firefox?
There is an option Block pop-up windows under the heading Permissions on the Privacy & Security page of Settings. The setting in the page information window is Open pop-up windows. There is an option Block pop-up windows under the heading Permissions on the Privacy & Security page of Settings.