It’s a real forehead-slapper that I only now started using Tab Mix Plus, a Firefox Extension that lets you completely customize Firefox’s tab behavior. It has about a billion settings, but the defaults are carefully chosen so that it does good stuff without needing adjustment. Unless you’re a goofball, you will notice an immediate improvement in browsing.
Among the more useful features are:
Session management - If you quit Firefox (or it crashes), Tab Mix Plus can restore your session when you restart.
Sensible forking - If you “fork” a tab, the new tab appears next to its parent, not at the end of the tab bar. As a result, related tabs are clustered, not scattered, and the ordering of tabs corresponds with your brain’s picture of the session. (Also, you can drag tabs, should you want to impose another ordering.)
I’m-new highlights - Tabs you fork into the background are highlighted to let you know they contain new, unseen content. This is great for power sessions when you otherwise couldn’t remember which tabs you’ve already seen.
Locking/Protecting - Lock a tab, and the browser won’t change it. If you click a link or do anything else that would replace the contents of the tab, it will fork a new tab instead. Protect a tab, and you can’t accidentally close it; you must unprotect it first.
If you use Firefox, you need to check out Tab Mix Plus. It’s good stuff.