1/200 is your camera's flash sync speed. It is the fastest shutter speed you SHOULD use with flash.

There are special modes you can enable which will let you shoot at faster then your sync speed - Canon calls it high Speed/FP flash sync. There are problems that arise with enabling high speed modes. The biggest one is that not all of the light from the flash will contribute to the exposure, which will impact your ability to properly light up your subject.

For more information see: [The Importance of Flash Sync Speed][1].


  [1]: http://www.kenrockwell.com/tech/syncspeed.htm