If you are a kinda person who prefer using a keyboard over mouse then Youtube gives you an easy way to forward or backward Youtube's videos.
You can use keyboard's number keys 0-9 to skip through Youtube videos, Every Youtube video is divided in 10 parts. By pressing 0 button you will take to starting point of video, 1 forward the video to 10% and 2 to 20% similarly 9 forward the video to 90%.
The procedure to use number keys as shortcut is you must first click the Youtube video, choice is your what you prefer mouse or keyboard shortcut to forward/backward Youtube video.
Note: Only main keys working for it (Num keys will not work).