Nope sorry. Bits being turned on are the read bits. If you look at a file (or directory) in unix, you see way on the left the permissions. You'll have 10 positions. The first one generally identifies a file as "directory" and you'll have a 'd' in that position (there are others but
most of the time you won't have to deal with them). In the next three positions are the user bits and show what permissions the owner of the file has. Next three are the group bits which shows group permissions and the last three are the world bits which shows what everyone has access to.
Each octet is a simple binary number but is depicted with rwx. Read, Write and Execute. If you know binary, the end position when it's on is '1', the center one is '2' and the left one is '4'. So 777 is the same rwxrwxrwx. 755 is rwxr-xr-x, a more common permissions setting for a script and 644 (rw-r--r--) is more common for a data or text file.
Your first command is something like doing a chmod 444 . and then a chmod 222 logo.gif etc... Unfortunately if you have a file in a subdirectory that has 755 for a specific reason, running those chmod commands will that script (and it's probably a script) from running since the execute bit is now off. That's why you use the a+r and/or a+w switches vs 444 or 222. The scripts and data that have a specific permission for a reason will at least maintain that permission and if it doesn't already have read or write, it's modified to add that permission.
Make sense? I can try to be clearer. You can also go to google and do a search on "man chmod". Lots and lots of man pages on the 'net
Carl