Are you talking about rubberbanding? Your character's polys sometimes get unsynced from the server so on the map (which is running on your computer) you keep moving and exploring it...but your connection to the server hasn't moved. Common in online games that require you to connect to a server hundreds of miles away. Not ArenaNet's fault.
And this is why you must train your eye to adequate and effectively distinquish when you are and are not rubberbanded. This is also why I have a macro on my G11 keyboard to /stuck the monent I press it. :3