Improve YouTube Performance in Firefox:

Does YouTube often pause and freeze when you’re watching a video? Here’s a trick that can fix the problem if you browse the web with Firefox. 

YouTube accounts for a significant portion of my online activity, so I’m naturally frustrated if it doesn’t work properly. Almost every video I watch pauses after 3 seconds or requires me to play, press pause, and wait 5 minutes until the video has fully loaded before I even attempt to play it. Turns out this and other playback problems of YouTube or Flash videos may be caused by Firefox’s restore feature.
Firefox maintains a restore features that backsup your tabs and content every 10 seconds. This is great if Firefox is closed prematurely but can cause problem when trying to watch Flash-based video streams. Though I love being able to return to a previous session when I close the browser, I’d like to be able to watch videos without headaches.
Here’s a plain English tutorial for how to adjust Firefox session restore.
1. Open Firefox and in the address bar, type “about:config”
You will see a message warning you that changing the advanced settings could affect your browser’s performance. This is true as a whole, but you have little to fear in this instince. Click “I’ll be good, I promise” button and continue.
2. Click on the Filter text-entry bar and type “browser.sessionstore.interval”
You should now see all other labels removed except for sessionstore.
3. Double-click on value and change it from “10000″ to “120000″
This changes Firefox from saving your session every 10 seconds to every 2 minutes. The value is stored in milliseconds, so if you want to change the autosave time, just convert the number into milliseconds (1 minute = 60,000 milliseconds).
4. Visit YouTube and confirm success
After entering your new value, visit a YouTube video that previously gave you trouble. If it plays more smoothly, enjoy! If problems continue, make sure you have installed the latest version of Flash or visit the Mozilla Support Forum for more assistance.
Also, it’s a good idea to limit the number of tabs open at once!