More about: config settings

network.prefetch-next > false

Disables the background downloading of websites. See the Link Prefetching FAQ

browser.backspace_action > 0

Backspace goes back on page at a time on the session history.

browser.tabs.tabMinWidth > 0

Needs Firefox restart, disables the "tab scrolling" (and the arrows at the extremes), the tabs with simply reduce their size to squeeze fit onto your screen.