You might not be running as root and root is most likely owner - which disallows you the right to change permissions. execute the following
cd /var
su
"enter password for root"
chown -R john www or /www
now maybe after successful
chmod -R 775 www or /www
A little info:
chown allows for changing the owner - you must be root to change the ownership if root is the owner :)
chmod 775 does this U+G+O User+Group+Others 7 = read write execute 5 = read and execute
change john to YOUR username (the one you log in as)
-R tells the commands to make the internal files of the directory "owned" by John as well.
read =1 write=2 execute=4 for a total of 7 for all permissions granted to UGO would be 777 (NOT recommended)
Hope this helps

Conrad