Website vs. local

That  is an existing issue with the java player used on the site.

However, in my experience, a lot of the trouble that studnts have with timing has to do with how they trigger events. Trying to sync things up with the "timer" or with they "wait___ sec" blocks will typically suffer from some sort of lag.  On the hand, chaining a series of events together with the "boadcast," or "broadcast and wait," blocks will help a lot. This tutorial on creating dialog may help clarify what I am describing.