Invalid .iwd files referenced

I got a problem but first of all I'm trying to host this on AlterIWNet.
I got an existing zombie mod where I wanted to remove a ramp.
I deleted the line which contained the ramp.
But when I started the game it said:"Impure client detected. Invalid .IWD files referenced."

So my question is: Is there any special method to change a mod? And is there a method to pack a mod? or can I just rar it and name it ****.iwd?

No, don't use rar.. it's compressing... Use Zip.

That error means that you're using wrong iwd's, mostly common when making a skin mod...

It worked. THANK YOU SO MUCH!
The difference between .rar and .zip was 3 kB.
When i tried it i couldn't believe it since Zip is also a compression format.