Current frame's properties can be viewed and modified by using Frame>Properties menu item.You can also double click on a frame with the mouse eft button.
  Delay: It is the delay (in 1/100ths of a second) following the displaying of the frame before the next frame is shown.
  Interlacing: Interlacing is a method for storing a GIF image so that it can be displayed progressively as it is downloaded; it does not significantly affect the size of the GIF file and depending on the displaying browser may be ignored for all but the first image in an animation. This flag be toggled on or off in either the dialog or the toolbar.
  Warning: Both Microsoft and Netscape browsers sometimes do not handle interlacing properly in an animation, showing black horizontal stripes during playback. It's a good idea to avoid interlacing within an animation.