Script Summary: Remove the white bar that pops up on the bottom of Youtube video pages, & disables auto "play next". Works in Chrome, Opera, Firefox (w/ Greasemonkey), & Safari (w/ Greasekit).
Youtube added a bar to the bottom of pages for videos in a list, like your favorites or playlists. It's triggered far too easily, in my opinion, often covering the video or some other link you were meaning to click. This script removes it, and also disables the auto "play next" feature.
To Re-Enable Autoplay
If you want the next video in a playlist to automatically play, follow these steps (note that you can always toggle autoplay; this just affects the default behavior):
Edit the source (Manage User Scripts..., select this script, then press Edit at the lower-left corner), and change "var disableAutoplay = true;" to "var disableAutoplay = false;". In the future I'll probably just turn this into a separate script.
Fixed the script to work again. Might add some more options in the future, if I ever get around to it.
Changed how autoplay is handled. It now displays a button in the top right corner of the page for videos that are in a playlist. You can click this button to toggle whether or not the next video autoplays, with 'Off' being the default behavior. This also got rid of the redirect script, so you should no longer have problems with your browser's back button.
Update 2: Changed the default behavior to disable autoplay. It can still be toggled by editing the script.
Update 1: Added the option to disable autoplay of the next video. It's off by default, but you can make an edit to the script to enable it (set disableAutoplay to true).