Im getting this message when I load up my game..

Script 'Pub_Huntaar_Loups' in file 'Vanheim.esp' has not been compiled.

How can I stop it?

You have to compile the said script in the CS.

Open the mod in CS and look for the script 'Pub_Huntaar_Loups'. Save the script and save the mod. Th error should disappear.