Flash videos do not generally allow FF or back. If you want to skip, just drag the button on the seeker bar to where you want to be.
This has little to do with codecs and more to do with how Flash movies are made.
I have the latest version of Klite installed. I want to watch all my movies and videos with windows media player. When it plays avi or other generic files I am able to fast forward and skip to sections within a video while it is playing but when I am playing .flv or .mkv it plays the videos however I am not able to fast forward to skip to a particular section. What is the use of installing codecs then? Plz help