How to skin terrain like grass?

hey i have some questions about skinning the w3 terrain.

I have opened the w3 vieuwer an exported the ashenvale dirty grass.
Then i change the texture from it and export it back in the vieuwer.
Then i was looking at both of the files and i saw that the original haves many holes in it and other things that wasnt there in the one i exported.

I thought it was nothing so i wanted to try it in the worl edior with the path: Ashen_DirtGrass.blp but it doenst change in the texture what did i do wrong??

I was wrong the path was differend now it really works in the world editor.
But i still got one problem the original skinn in the w3vieuwer is differend then when i export it, try it out and you will see.