Help! with a terrain1.gif

[Qages]

Help i made a terrain1.gif and its not working it saz "image not 640 x 480 x 256 color". i dont know whats wrong; i saved it in 265 and it is 640 x 480 ! please help
im attaching the gif i used and the bitmap i used to make it. can you please see whats wrong with the gif and can you please save the bitmap as a gif in the rite format?
thx

 

[Prometeus]

green, cyan violet and dark grey must be the last three colours of the palette, if you want this file to work...