If you want to make sure that you don't accidentally move track, you can glue it down!
To glue track
Method 1:

Method 2:

If you want to know whether track is glued, hover over it, and look in the Status Bar:

NOTE: If you glue one piece of track, all connected track is glued as well.
TIP: To move glued track, hold the SHIFT key down when dragging. The track will be unglued automatically.
Page url: http://www.anyrail.com/help_en/index.html?gluing_track.htm