OK, this involves a little techo-speak, but really not much.  A client gave me some feedback about his films, which he loved. He has two computers at his home.  One is a laptop, connecting wirelessly.  One is plugged into the router.  He noticed that on one the film played back fine. On the other the same film was a little jerky.  He wondered why that was? Well without seeing the spec from the computers I can only guess but – all other things being even – there’s a good chance that the laptop was the jerky one.  Generally speaking a wireless connection is not as fast as a wired broadband connection.  When you watch a film over the internet the information that comprises that film is obviously not stored on your own computer.  It’s somewhere else and needs to be ’streamed’ to your computer to enable playback.  The faster the connection, the faster that information can stream.  That’s important with video because video involves a lot of information (as compared to, say, audio in MP3 format).  So the faster the connection the more likely that information can be fed into your computer at the rate it’s required to produce smooth playback.  So one key reason that a video can be jerky is the connection speed to the internet.  Of course, other factors can be involved, like the processing power of the computer itself (if it is budget, old processor it could struggle), and a critical factor, the size of the video itself.  The size of the video is determined by its duration (is it a feature-length movie, etc) but also, crucially, its resolution (the size of the image and the way it has been compressed).  So when you are trying to produce films for the internet that will stream satisfactorily for the maximum number of people you clearly want short films at minimum resolution.  Simple, right?  But the problem with that is low resolution can look rubbish!  So, like so much in life, it’s all about compromise.